diff --git a/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart b/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
index d6c3eca24e0..d818e4d07a2 100644
--- a/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
+++ b/pkg/front_end/lib/src/fasta/builder/procedure_builder.dart
@@ -6,6 +6,7 @@ library fasta.procedure_builder;
 
 import 'dart:core' hide MapEntry;
 
+import 'package:front_end/src/fasta/kernel/kernel_api.dart';
 import 'package:kernel/ast.dart' hide Variance;
 
 import 'package:kernel/type_algebra.dart';
@@ -361,6 +362,27 @@ abstract class FunctionBuilder extends MemberBuilder {
     return function = result;
   }
 
+  /// Returns the [index]th parameter of this function.
+  ///
+  /// The index is the syntactical index, including both positional and named
+  /// parameter in the order they are declared, and excluding the synthesized
+  /// this parameter on extension instance members.
+  VariableDeclaration getFormalParameter(int index) {
+    if (isExtensionInstanceMember) {
+      return formals[index + 1].variable;
+    } else {
+      return formals[index].variable;
+    }
+  }
+
+  /// If this is an extension instance method, the tear off closure parameter
+  /// corresponding to the [index]th parameter on the instance method is
+  /// returned.
+  ///
+  /// This is used to update the default value for the closure parameter when
+  /// it has been computed for the original parameter.
+  VariableDeclaration getExtensionTearOffParameter(int index) => null;
+
   /// Returns the parameter for 'this' synthetically added to extension
   /// instance members.
   VariableDeclaration get extensionThis {
@@ -451,6 +473,14 @@ class ProcedureBuilder extends FunctionBuilder {
   /// the synthetically created tear off function.
   Procedure _extensionTearOff;
 
+  /// If this is an extension instance method then
+  /// [_extensionTearOffParameterMap] holds a map from the parameters of
+  /// the methods to the parameter of the closure returned in the tear-off.
+  ///
+  /// This map is used to set the default values on the closure parameters when
+  /// these have been built.
+  Map<VariableDeclaration, VariableDeclaration> _extensionTearOffParameterMap;
+
   ProcedureBuilder(
       List<MetadataBuilder> metadata,
       int modifiers,
@@ -585,6 +615,8 @@ class ProcedureBuilder extends FunctionBuilder {
         _extensionTearOff != null, "No extension tear off created for $this.");
     if (_extensionTearOff.name != null) return;
 
+    _extensionTearOffParameterMap = {};
+
     int fileOffset = _procedure.fileOffset;
 
     int extensionTypeParameterCount =
@@ -592,17 +624,18 @@ class ProcedureBuilder extends FunctionBuilder {
 
     List<TypeParameter> typeParameters = <TypeParameter>[];
 
+    Map<TypeParameter, DartType> substitutionMap = {};
     List<DartType> typeArguments = <DartType>[];
     for (TypeParameter typeParameter in function.typeParameters) {
       TypeParameter newTypeParameter = new TypeParameter(typeParameter.name);
       typeParameters.add(newTypeParameter);
-      typeArguments.add(new TypeParameterType(newTypeParameter));
+      typeArguments.add(substitutionMap[typeParameter] =
+          new TypeParameterType(newTypeParameter));
     }
 
     List<TypeParameter> tearOffTypeParameters = <TypeParameter>[];
     List<TypeParameter> closureTypeParameters = <TypeParameter>[];
-    Substitution substitution =
-        Substitution.fromPairs(function.typeParameters, typeArguments);
+    Substitution substitution = Substitution.fromMap(substitutionMap);
     for (int index = 0; index < typeParameters.length; index++) {
       TypeParameter newTypeParameter = typeParameters[index];
       newTypeParameter.bound =
@@ -618,12 +651,11 @@ class ProcedureBuilder extends FunctionBuilder {
     VariableDeclaration copyParameter(
         VariableDeclaration parameter, DartType type,
         {bool isOptional}) {
-      // TODO(johnniwinther): Handle default values.
-      return new VariableDeclaration(parameter.name,
-          type: type,
-          initializer: isOptional ? new NullLiteral() : null,
-          isFinal: parameter.isFinal)
+      VariableDeclaration newParameter = new VariableDeclaration(parameter.name,
+          type: type, isFinal: parameter.isFinal)
         ..fileOffset = parameter.fileOffset;
+      _extensionTearOffParameterMap[parameter] = newParameter;
+      return newParameter;
     }
 
     VariableDeclaration extensionThis = copyParameter(
@@ -697,6 +729,14 @@ class ProcedureBuilder extends FunctionBuilder {
     _extensionTearOff.function.parent = _extensionTearOff;
   }
 
+  @override
+  VariableDeclaration getExtensionTearOffParameter(int index) {
+    if (_extensionTearOffParameterMap != null) {
+      return _extensionTearOffParameterMap[getFormalParameter(index)];
+    }
+    return null;
+  }
+
   /// The [Procedure] built by this builder.
   Procedure get procedure => isPatch ? origin.procedure : _procedure;
 
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 9b9e060b74a..980cceba539 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -789,18 +789,31 @@ class BodyBuilder extends ScopeListener<JumpTarget>
         FormalParameterBuilder parameter = formals.parameters[i];
         Expression initializer = parameter.target.initializer;
         if (parameter.isOptional || initializer != null) {
-          VariableDeclaration realParameter = builder.formals[i].target;
           if (parameter.isOptional) {
             initializer ??= forest.createNullLiteral(
-                // TODO(ahe): Should store: realParameter.fileOffset
+                // TODO(ahe): Should store: originParameter.fileOffset
                 // https://github.com/dart-lang/sdk/issues/32289
                 null);
           }
-          realParameter.initializer = initializer..parent = realParameter;
+          VariableDeclaration originParameter = builder.getFormalParameter(i);
+          originParameter.initializer = initializer..parent = originParameter;
           typeInferrer?.inferParameterInitializer(
-              this, initializer, realParameter.type);
+              this, initializer, originParameter.type);
           libraryBuilder.loader.transformPostInference(
-              realParameter, transformSetLiterals, transformCollections);
+              originParameter, transformSetLiterals, transformCollections);
+
+          VariableDeclaration extensionTearOffParameter =
+              builder.getExtensionTearOffParameter(i);
+          if (extensionTearOffParameter != null) {
+            cloner ??= new CloneVisitor();
+            Expression tearOffInitializer = cloner.clone(initializer);
+            extensionTearOffParameter.initializer = tearOffInitializer
+              ..parent = extensionTearOffParameter;
+            libraryBuilder.loader.transformPostInference(
+                extensionTearOffParameter,
+                transformSetLiterals,
+                transformCollections);
+          }
         }
       }
     }
diff --git a/pkg/front_end/testcases/extensions/default_values.dart b/pkg/front_end/testcases/extensions/default_values.dart
new file mode 100644
index 00000000000..0b08f6de232
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/default_values.dart
@@ -0,0 +1,36 @@
+// Copyright (c) 2019, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class Class {}
+
+extension Extension on Class {
+  method0([a]) => a;
+  method1([a = 42]) => a;
+  method2({b = 87}) => b;
+  method3({c = staticMethod}) => c();
+  static staticMethod() => 123;
+}
+
+main() {
+  Class c = new Class();
+  var tearOff0 = c.method0;
+  expect(0, tearOff0(0));
+  expect(null, tearOff0());
+  var tearOff1 = c.method1;
+  expect(0, tearOff1(0));
+  expect(42, tearOff1());
+  var tearOff2 = c.method2;
+  expect(0, tearOff2(b: 0));
+  expect(87, tearOff2());
+  var tearOff3 = c.method3;
+  expect(0, tearOff3(c: () => 0));
+  expect(123, tearOff3());
+}
+
+
+expect(expected, actual) {
+  if (expected != actual) {
+    throw 'Mismatch: expected=$expected, actual=$actual';
+  }
+}
\ No newline at end of file
diff --git a/pkg/front_end/testcases/extensions/default_values.dart.outline.expect b/pkg/front_end/testcases/extensions/default_values.dart.outline.expect
new file mode 100644
index 00000000000..77ed4f468f7
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/default_values.dart.outline.expect
@@ -0,0 +1,41 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    ;
+}
+extension Extension on self::Class* {
+  method method0 = self::Extension|method0;
+  tearoff method0 = self::Extension|get#method0;
+  method method1 = self::Extension|method1;
+  tearoff method1 = self::Extension|get#method1;
+  method method2 = self::Extension|method2;
+  tearoff method2 = self::Extension|get#method2;
+  method method3 = self::Extension|method3;
+  tearoff method3 = self::Extension|get#method3;
+  static method staticMethod = self::Extension|staticMethod;
+}
+static method Extension|method0(final self::Class* #this, [dynamic a]) → dynamic
+  ;
+static method Extension|get#method0(final self::Class* #this) → ([dynamic]) →* dynamic
+  return ([dynamic a]) → dynamic => self::Extension|method0(#this, a);
+static method Extension|method1(final self::Class* #this, [dynamic a]) → dynamic
+  ;
+static method Extension|get#method1(final self::Class* #this) → ([dynamic]) →* dynamic
+  return ([dynamic a]) → dynamic => self::Extension|method1(#this, a);
+static method Extension|method2(final self::Class* #this, {dynamic b}) → dynamic
+  ;
+static method Extension|get#method2(final self::Class* #this) → ({b: dynamic}) →* dynamic
+  return ({dynamic b}) → dynamic => self::Extension|method2(#this, b: b);
+static method Extension|method3(final self::Class* #this, {dynamic c}) → dynamic
+  ;
+static method Extension|get#method3(final self::Class* #this) → ({c: dynamic}) →* dynamic
+  return ({dynamic c}) → dynamic => self::Extension|method3(#this, c: c);
+static method Extension|staticMethod() → dynamic
+  ;
+static method main() → dynamic
+  ;
+static method expect(dynamic expected, dynamic actual) → dynamic
+  ;
diff --git a/pkg/front_end/testcases/extensions/default_values.dart.strong.expect b/pkg/front_end/testcases/extensions/default_values.dart.strong.expect
new file mode 100644
index 00000000000..e6b8869400f
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/default_values.dart.strong.expect
@@ -0,0 +1,65 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    : super core::Object::•()
+    ;
+}
+extension Extension on self::Class* {
+  method method0 = self::Extension|method0;
+  tearoff method0 = self::Extension|get#method0;
+  method method1 = self::Extension|method1;
+  tearoff method1 = self::Extension|get#method1;
+  method method2 = self::Extension|method2;
+  tearoff method2 = self::Extension|get#method2;
+  method method3 = self::Extension|method3;
+  tearoff method3 = self::Extension|get#method3;
+  static method staticMethod = self::Extension|staticMethod;
+}
+static method Extension|method0(final self::Class* #this, [dynamic a = #C1]) → dynamic
+  return a;
+static method Extension|get#method0(final self::Class* #this) → ([dynamic]) →* dynamic
+  return ([dynamic a = #C1]) → dynamic => self::Extension|method0(#this, a);
+static method Extension|method1(final self::Class* #this, [dynamic a = #C2]) → dynamic
+  return a;
+static method Extension|get#method1(final self::Class* #this) → ([dynamic]) →* dynamic
+  return ([dynamic a = #C2]) → dynamic => self::Extension|method1(#this, a);
+static method Extension|method2(final self::Class* #this, {dynamic b = #C3}) → dynamic
+  return b;
+static method Extension|get#method2(final self::Class* #this) → ({b: dynamic}) →* dynamic
+  return ({dynamic b = #C3}) → dynamic => self::Extension|method2(#this, b: b);
+static method Extension|method3(final self::Class* #this, {dynamic c = #C4}) → dynamic
+  return c.call();
+static method Extension|get#method3(final self::Class* #this) → ({c: dynamic}) →* dynamic
+  return ({dynamic c = #C4}) → dynamic => self::Extension|method3(#this, c: c);
+static method Extension|staticMethod() → dynamic
+  return 123;
+static method main() → dynamic {
+  self::Class* c = new self::Class::•();
+  ([dynamic]) →* dynamic tearOff0 = self::Extension|get#method0(c);
+  self::expect(0, tearOff0.call(0));
+  self::expect(null, tearOff0.call());
+  ([dynamic]) →* dynamic tearOff1 = self::Extension|get#method1(c);
+  self::expect(0, tearOff1.call(0));
+  self::expect(42, tearOff1.call());
+  ({b: dynamic}) →* dynamic tearOff2 = self::Extension|get#method2(c);
+  self::expect(0, tearOff2.call(b: 0));
+  self::expect(87, tearOff2.call());
+  ({c: dynamic}) →* dynamic tearOff3 = self::Extension|get#method3(c);
+  self::expect(0, tearOff3.call(c: () → core::int* => 0));
+  self::expect(123, tearOff3.call());
+}
+static method expect(dynamic expected, dynamic actual) → dynamic {
+  if(!expected.{core::Object::==}(actual)) {
+    throw "Mismatch: expected=${expected}, actual=${actual}";
+  }
+}
+
+constants  {
+  #C1 = null
+  #C2 = 42
+  #C3 = 87
+  #C4 = tearoff self::Extension|staticMethod
+}
diff --git a/pkg/front_end/testcases/extensions/default_values.dart.strong.transformed.expect b/pkg/front_end/testcases/extensions/default_values.dart.strong.transformed.expect
new file mode 100644
index 00000000000..e6b8869400f
--- /dev/null
+++ b/pkg/front_end/testcases/extensions/default_values.dart.strong.transformed.expect
@@ -0,0 +1,65 @@
+library;
+import self as self;
+import "dart:core" as core;
+
+class Class extends core::Object {
+  synthetic constructor •() → self::Class*
+    : super core::Object::•()
+    ;
+}
+extension Extension on self::Class* {
+  method method0 = self::Extension|method0;
+  tearoff method0 = self::Extension|get#method0;
+  method method1 = self::Extension|method1;
+  tearoff method1 = self::Extension|get#method1;
+  method method2 = self::Extension|method2;
+  tearoff method2 = self::Extension|get#method2;
+  method method3 = self::Extension|method3;
+  tearoff method3 = self::Extension|get#method3;
+  static method staticMethod = self::Extension|staticMethod;
+}
+static method Extension|method0(final self::Class* #this, [dynamic a = #C1]) → dynamic
+  return a;
+static method Extension|get#method0(final self::Class* #this) → ([dynamic]) →* dynamic
+  return ([dynamic a = #C1]) → dynamic => self::Extension|method0(#this, a);
+static method Extension|method1(final self::Class* #this, [dynamic a = #C2]) → dynamic
+  return a;
+static method Extension|get#method1(final self::Class* #this) → ([dynamic]) →* dynamic
+  return ([dynamic a = #C2]) → dynamic => self::Extension|method1(#this, a);
+static method Extension|method2(final self::Class* #this, {dynamic b = #C3}) → dynamic
+  return b;
+static method Extension|get#method2(final self::Class* #this) → ({b: dynamic}) →* dynamic
+  return ({dynamic b = #C3}) → dynamic => self::Extension|method2(#this, b: b);
+static method Extension|method3(final self::Class* #this, {dynamic c = #C4}) → dynamic
+  return c.call();
+static method Extension|get#method3(final self::Class* #this) → ({c: dynamic}) →* dynamic
+  return ({dynamic c = #C4}) → dynamic => self::Extension|method3(#this, c: c);
+static method Extension|staticMethod() → dynamic
+  return 123;
+static method main() → dynamic {
+  self::Class* c = new self::Class::•();
+  ([dynamic]) →* dynamic tearOff0 = self::Extension|get#method0(c);
+  self::expect(0, tearOff0.call(0));
+  self::expect(null, tearOff0.call());
+  ([dynamic]) →* dynamic tearOff1 = self::Extension|get#method1(c);
+  self::expect(0, tearOff1.call(0));
+  self::expect(42, tearOff1.call());
+  ({b: dynamic}) →* dynamic tearOff2 = self::Extension|get#method2(c);
+  self::expect(0, tearOff2.call(b: 0));
+  self::expect(87, tearOff2.call());
+  ({c: dynamic}) →* dynamic tearOff3 = self::Extension|get#method3(c);
+  self::expect(0, tearOff3.call(c: () → core::int* => 0));
+  self::expect(123, tearOff3.call());
+}
+static method expect(dynamic expected, dynamic actual) → dynamic {
+  if(!expected.{core::Object::==}(actual)) {
+    throw "Mismatch: expected=${expected}, actual=${actual}";
+  }
+}
+
+constants  {
+  #C1 = null
+  #C2 = 42
+  #C3 = 87
+  #C4 = tearoff self::Extension|staticMethod
+}
diff --git a/pkg/front_end/testcases/extensions/direct_instance_access.dart.outline.expect b/pkg/front_end/testcases/extensions/direct_instance_access.dart.outline.expect
index 86ff6e693a1..f38f7f8cb68 100644
--- a/pkg/front_end/testcases/extensions/direct_instance_access.dart.outline.expect
+++ b/pkg/front_end/testcases/extensions/direct_instance_access.dart.outline.expect
@@ -76,11 +76,11 @@ static method Extension|get#writeSetterRequired(final self::Class* #this) → (d
 static method Extension|writeSetterOptional(final self::Class* #this, [dynamic value]) → dynamic
   ;
 static method Extension|get#writeSetterOptional(final self::Class* #this) → ([dynamic]) →* dynamic
-  return ([dynamic value = null]) → dynamic => self::Extension|writeSetterOptional(#this, value);
+  return ([dynamic value]) → dynamic => self::Extension|writeSetterOptional(#this, value);
 static method Extension|writeSetterNamed(final self::Class* #this, {dynamic value}) → dynamic
   ;
 static method Extension|get#writeSetterNamed(final self::Class* #this) → ({value: dynamic}) →* dynamic
-  return ({dynamic value = null}) → dynamic => self::Extension|writeSetterNamed(#this, value: value);
+  return ({dynamic value}) → dynamic => self::Extension|writeSetterNamed(#this, value: value);
 static method Extension|get#tearOffGetterNoArgs(final self::Class* #this) → dynamic
   ;
 static method Extension|get#tearOffGetterRequired(final self::Class* #this) → dynamic
@@ -116,11 +116,11 @@ static method GenericExtension|get#writeSetterRequired<T extends core::Object* =
 static method GenericExtension|writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterOptional::T*>* #this, [self::GenericExtension|writeSetterOptional::T* value]) → dynamic
   ;
 static method GenericExtension|get#writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterOptional::T*>* #this) → ([self::GenericExtension|get#writeSetterOptional::T*]) →* dynamic
-  return ([self::GenericExtension|get#writeSetterOptional::T* value = null]) → dynamic => self::GenericExtension|writeSetterOptional<self::GenericExtension|get#writeSetterOptional::T*>(#this, value);
+  return ([self::GenericExtension|get#writeSetterOptional::T* value]) → dynamic => self::GenericExtension|writeSetterOptional<self::GenericExtension|get#writeSetterOptional::T*>(#this, value);
 static method GenericExtension|writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterNamed::T*>* #this, {self::GenericExtension|writeSetterNamed::T* value}) → dynamic
   ;
 static method GenericExtension|get#writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterNamed::T*>* #this) → ({value: self::GenericExtension|get#writeSetterNamed::T*}) →* dynamic
-  return ({self::GenericExtension|get#writeSetterNamed::T* value = null}) → dynamic => self::GenericExtension|writeSetterNamed<self::GenericExtension|get#writeSetterNamed::T*>(#this, value: value);
+  return ({self::GenericExtension|get#writeSetterNamed::T* value}) → dynamic => self::GenericExtension|writeSetterNamed<self::GenericExtension|get#writeSetterNamed::T*>(#this, value: value);
 static method GenericExtension|genericWriteSetterRequired<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterRequired::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterRequired::T*>* #this, self::GenericExtension|genericWriteSetterRequired::S* value) → dynamic
   ;
 static method GenericExtension|get#genericWriteSetterRequired<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterRequired::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterRequired::T* = dynamic>(S*) →* dynamic
@@ -128,9 +128,9 @@ static method GenericExtension|get#genericWriteSetterRequired<T extends core::Ob
 static method GenericExtension|genericWriteSetterOptional<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterOptional::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterOptional::T*>* #this, [self::GenericExtension|genericWriteSetterOptional::S* value]) → dynamic
   ;
 static method GenericExtension|get#genericWriteSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterOptional::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterOptional::T* = dynamic>([S*]) →* dynamic
-  return <S extends self::GenericExtension|get#genericWriteSetterOptional::T* = dynamic>([S* value = null]) → dynamic => self::GenericExtension|genericWriteSetterOptional<self::GenericExtension|get#genericWriteSetterOptional::T*, S*>(#this, value);
+  return <S extends self::GenericExtension|get#genericWriteSetterOptional::T* = dynamic>([S* value]) → dynamic => self::GenericExtension|genericWriteSetterOptional<self::GenericExtension|get#genericWriteSetterOptional::T*, S*>(#this, value);
 static method GenericExtension|get#genericWriteSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterNamed::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterNamed::T* = dynamic>({value: S*}) →* dynamic
-  return <S extends self::GenericExtension|get#genericWriteSetterNamed::T* = dynamic>({S* value = null}) → dynamic => self::GenericExtension|genericWriteSetterNamed<self::GenericExtension|get#genericWriteSetterNamed::T*, S*>(#this, value: value);
+  return <S extends self::GenericExtension|get#genericWriteSetterNamed::T* = dynamic>({S* value}) → dynamic => self::GenericExtension|genericWriteSetterNamed<self::GenericExtension|get#genericWriteSetterNamed::T*, S*>(#this, value: value);
 static method GenericExtension|genericWriteSetterNamed<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterNamed::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterNamed::T*>* #this, {self::GenericExtension|genericWriteSetterNamed::S* value}) → dynamic
   ;
 static method GenericExtension|get#property<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#property::T*>* #this) → self::GenericExtension|get#property::T*
diff --git a/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.expect b/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.expect
index 5cdf5f93754..ee8966fee81 100644
--- a/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.expect
+++ b/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.expect
@@ -77,12 +77,12 @@ static method Extension|writeSetterRequired(final self::Class* #this, dynamic va
 }
 static method Extension|get#writeSetterRequired(final self::Class* #this) → (dynamic) →* dynamic
   return (dynamic value) → dynamic => self::Extension|writeSetterRequired(#this, value);
-static method Extension|writeSetterOptional(final self::Class* #this = #C1, [dynamic value = #C1]) → dynamic {
+static method Extension|writeSetterOptional(final self::Class* #this, [dynamic value = #C1]) → dynamic {
   self::Extension|set#property(#this, value);
 }
 static method Extension|get#writeSetterOptional(final self::Class* #this) → ([dynamic]) →* dynamic
   return ([dynamic value = #C1]) → dynamic => self::Extension|writeSetterOptional(#this, value);
-static method Extension|writeSetterNamed(final self::Class* #this = #C1, {dynamic value = #C1}) → dynamic {
+static method Extension|writeSetterNamed(final self::Class* #this, {dynamic value = #C1}) → dynamic {
   self::Extension|set#property(#this, value);
 }
 static method Extension|get#writeSetterNamed(final self::Class* #this) → ({value: dynamic}) →* dynamic
@@ -144,12 +144,12 @@ static method GenericExtension|writeSetterRequired<T extends core::Object* = dyn
 }
 static method GenericExtension|get#writeSetterRequired<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterRequired::T*>* #this) → (self::GenericExtension|get#writeSetterRequired::T*) →* dynamic
   return (self::GenericExtension|get#writeSetterRequired::T* value) → dynamic => self::GenericExtension|writeSetterRequired<self::GenericExtension|get#writeSetterRequired::T*>(#this, value);
-static method GenericExtension|writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterOptional::T*>* #this = #C1, [self::GenericExtension|writeSetterOptional::T* value = #C1]) → dynamic {
+static method GenericExtension|writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterOptional::T*>* #this, [self::GenericExtension|writeSetterOptional::T* value = #C1]) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|writeSetterOptional::T*>(#this, value);
 }
 static method GenericExtension|get#writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterOptional::T*>* #this) → ([self::GenericExtension|get#writeSetterOptional::T*]) →* dynamic
   return ([self::GenericExtension|get#writeSetterOptional::T* value = #C1]) → dynamic => self::GenericExtension|writeSetterOptional<self::GenericExtension|get#writeSetterOptional::T*>(#this, value);
-static method GenericExtension|writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterNamed::T*>* #this = #C1, {self::GenericExtension|writeSetterNamed::T* value = #C1}) → dynamic {
+static method GenericExtension|writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterNamed::T*>* #this, {self::GenericExtension|writeSetterNamed::T* value = #C1}) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|writeSetterNamed::T*>(#this, value);
 }
 static method GenericExtension|get#writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterNamed::T*>* #this) → ({value: self::GenericExtension|get#writeSetterNamed::T*}) →* dynamic
@@ -159,14 +159,14 @@ static method GenericExtension|genericWriteSetterRequired<T extends core::Object
 }
 static method GenericExtension|get#genericWriteSetterRequired<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterRequired::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterRequired::T* = dynamic>(S*) →* dynamic
   return <S extends self::GenericExtension|get#genericWriteSetterRequired::T* = dynamic>(S* value) → dynamic => self::GenericExtension|genericWriteSetterRequired<self::GenericExtension|get#genericWriteSetterRequired::T*, S*>(#this, value);
-static method GenericExtension|genericWriteSetterOptional<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterOptional::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterOptional::T*>* #this = #C1, [self::GenericExtension|genericWriteSetterOptional::S* value = #C1]) → dynamic {
+static method GenericExtension|genericWriteSetterOptional<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterOptional::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterOptional::T*>* #this, [self::GenericExtension|genericWriteSetterOptional::S* value = #C1]) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|genericWriteSetterOptional::T*>(#this, value);
 }
 static method GenericExtension|get#genericWriteSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterOptional::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterOptional::T* = dynamic>([S*]) →* dynamic
   return <S extends self::GenericExtension|get#genericWriteSetterOptional::T* = dynamic>([S* value = #C1]) → dynamic => self::GenericExtension|genericWriteSetterOptional<self::GenericExtension|get#genericWriteSetterOptional::T*, S*>(#this, value);
 static method GenericExtension|get#genericWriteSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterNamed::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterNamed::T* = dynamic>({value: S*}) →* dynamic
   return <S extends self::GenericExtension|get#genericWriteSetterNamed::T* = dynamic>({S* value = #C1}) → dynamic => self::GenericExtension|genericWriteSetterNamed<self::GenericExtension|get#genericWriteSetterNamed::T*, S*>(#this, value: value);
-static method GenericExtension|genericWriteSetterNamed<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterNamed::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterNamed::T*>* #this = #C1, {self::GenericExtension|genericWriteSetterNamed::S* value = #C1}) → dynamic {
+static method GenericExtension|genericWriteSetterNamed<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterNamed::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterNamed::T*>* #this, {self::GenericExtension|genericWriteSetterNamed::S* value = #C1}) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|genericWriteSetterNamed::T*>(#this, value);
 }
 static method GenericExtension|get#property<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#property::T*>* #this) → self::GenericExtension|get#property::T*
diff --git a/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.transformed.expect b/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.transformed.expect
index 5cdf5f93754..ee8966fee81 100644
--- a/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/extensions/direct_instance_access.dart.strong.transformed.expect
@@ -77,12 +77,12 @@ static method Extension|writeSetterRequired(final self::Class* #this, dynamic va
 }
 static method Extension|get#writeSetterRequired(final self::Class* #this) → (dynamic) →* dynamic
   return (dynamic value) → dynamic => self::Extension|writeSetterRequired(#this, value);
-static method Extension|writeSetterOptional(final self::Class* #this = #C1, [dynamic value = #C1]) → dynamic {
+static method Extension|writeSetterOptional(final self::Class* #this, [dynamic value = #C1]) → dynamic {
   self::Extension|set#property(#this, value);
 }
 static method Extension|get#writeSetterOptional(final self::Class* #this) → ([dynamic]) →* dynamic
   return ([dynamic value = #C1]) → dynamic => self::Extension|writeSetterOptional(#this, value);
-static method Extension|writeSetterNamed(final self::Class* #this = #C1, {dynamic value = #C1}) → dynamic {
+static method Extension|writeSetterNamed(final self::Class* #this, {dynamic value = #C1}) → dynamic {
   self::Extension|set#property(#this, value);
 }
 static method Extension|get#writeSetterNamed(final self::Class* #this) → ({value: dynamic}) →* dynamic
@@ -144,12 +144,12 @@ static method GenericExtension|writeSetterRequired<T extends core::Object* = dyn
 }
 static method GenericExtension|get#writeSetterRequired<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterRequired::T*>* #this) → (self::GenericExtension|get#writeSetterRequired::T*) →* dynamic
   return (self::GenericExtension|get#writeSetterRequired::T* value) → dynamic => self::GenericExtension|writeSetterRequired<self::GenericExtension|get#writeSetterRequired::T*>(#this, value);
-static method GenericExtension|writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterOptional::T*>* #this = #C1, [self::GenericExtension|writeSetterOptional::T* value = #C1]) → dynamic {
+static method GenericExtension|writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterOptional::T*>* #this, [self::GenericExtension|writeSetterOptional::T* value = #C1]) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|writeSetterOptional::T*>(#this, value);
 }
 static method GenericExtension|get#writeSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterOptional::T*>* #this) → ([self::GenericExtension|get#writeSetterOptional::T*]) →* dynamic
   return ([self::GenericExtension|get#writeSetterOptional::T* value = #C1]) → dynamic => self::GenericExtension|writeSetterOptional<self::GenericExtension|get#writeSetterOptional::T*>(#this, value);
-static method GenericExtension|writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterNamed::T*>* #this = #C1, {self::GenericExtension|writeSetterNamed::T* value = #C1}) → dynamic {
+static method GenericExtension|writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|writeSetterNamed::T*>* #this, {self::GenericExtension|writeSetterNamed::T* value = #C1}) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|writeSetterNamed::T*>(#this, value);
 }
 static method GenericExtension|get#writeSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#writeSetterNamed::T*>* #this) → ({value: self::GenericExtension|get#writeSetterNamed::T*}) →* dynamic
@@ -159,14 +159,14 @@ static method GenericExtension|genericWriteSetterRequired<T extends core::Object
 }
 static method GenericExtension|get#genericWriteSetterRequired<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterRequired::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterRequired::T* = dynamic>(S*) →* dynamic
   return <S extends self::GenericExtension|get#genericWriteSetterRequired::T* = dynamic>(S* value) → dynamic => self::GenericExtension|genericWriteSetterRequired<self::GenericExtension|get#genericWriteSetterRequired::T*, S*>(#this, value);
-static method GenericExtension|genericWriteSetterOptional<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterOptional::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterOptional::T*>* #this = #C1, [self::GenericExtension|genericWriteSetterOptional::S* value = #C1]) → dynamic {
+static method GenericExtension|genericWriteSetterOptional<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterOptional::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterOptional::T*>* #this, [self::GenericExtension|genericWriteSetterOptional::S* value = #C1]) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|genericWriteSetterOptional::T*>(#this, value);
 }
 static method GenericExtension|get#genericWriteSetterOptional<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterOptional::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterOptional::T* = dynamic>([S*]) →* dynamic
   return <S extends self::GenericExtension|get#genericWriteSetterOptional::T* = dynamic>([S* value = #C1]) → dynamic => self::GenericExtension|genericWriteSetterOptional<self::GenericExtension|get#genericWriteSetterOptional::T*, S*>(#this, value);
 static method GenericExtension|get#genericWriteSetterNamed<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#genericWriteSetterNamed::T*>* #this) → <S extends self::GenericExtension|get#genericWriteSetterNamed::T* = dynamic>({value: S*}) →* dynamic
   return <S extends self::GenericExtension|get#genericWriteSetterNamed::T* = dynamic>({S* value = #C1}) → dynamic => self::GenericExtension|genericWriteSetterNamed<self::GenericExtension|get#genericWriteSetterNamed::T*, S*>(#this, value: value);
-static method GenericExtension|genericWriteSetterNamed<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterNamed::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterNamed::T*>* #this = #C1, {self::GenericExtension|genericWriteSetterNamed::S* value = #C1}) → dynamic {
+static method GenericExtension|genericWriteSetterNamed<T extends core::Object* = dynamic, S extends self::GenericExtension|genericWriteSetterNamed::T* = dynamic>(final self::GenericClass<self::GenericExtension|genericWriteSetterNamed::T*>* #this, {self::GenericExtension|genericWriteSetterNamed::S* value = #C1}) → dynamic {
   self::GenericExtension|set#property<self::GenericExtension|genericWriteSetterNamed::T*>(#this, value);
 }
 static method GenericExtension|get#property<T extends core::Object* = dynamic>(final self::GenericClass<self::GenericExtension|get#property::T*>* #this) → self::GenericExtension|get#property::T*
diff --git a/pkg/front_end/testcases/extensions/instance_members.dart.outline.expect b/pkg/front_end/testcases/extensions/instance_members.dart.outline.expect
index 36c0330f9e7..09050c71b62 100644
--- a/pkg/front_end/testcases/extensions/instance_members.dart.outline.expect
+++ b/pkg/front_end/testcases/extensions/instance_members.dart.outline.expect
@@ -37,11 +37,11 @@ static method A2|get#method2(final self::A1* #this) → <T extends core::Object*
 static method A2|method3<T extends core::Object* = dynamic>(final self::A1* #this, [self::A2|method3::T* o]) → self::A1*
   ;
 static method A2|get#method3(final self::A1* #this) → <T extends core::Object* = dynamic>([T*]) →* self::A1*
-  return <T extends core::Object* = dynamic>([T* o = null]) → self::A1* => self::A2|method3<T*>(#this, o);
+  return <T extends core::Object* = dynamic>([T* o]) → self::A1* => self::A2|method3<T*>(#this, o);
 static method A2|method4<T extends core::Object* = dynamic>(final self::A1* #this, {self::A2|method4::T* o}) → self::A1*
   ;
 static method A2|get#method4(final self::A1* #this) → <T extends core::Object* = dynamic>({o: T*}) →* self::A1*
-  return <T extends core::Object* = dynamic>({T* o = null}) → self::A1* => self::A2|method4<T*>(#this, o: o);
+  return <T extends core::Object* = dynamic>({T* o}) → self::A1* => self::A2|method4<T*>(#this, o: o);
 static method B2|method1<T extends core::Object* = dynamic>(final self::B1<self::B2|method1::T*>* #this) → self::B1<self::B2|method1::T*>*
   ;
 static method B2|get#method1<T extends core::Object* = dynamic>(final self::B1<self::B2|get#method1::T*>* #this) → () →* self::B1<self::B2|get#method1::T*>*
diff --git a/pkg/front_end/testcases/extensions/instance_members.dart.strong.expect b/pkg/front_end/testcases/extensions/instance_members.dart.strong.expect
index dfed3fb1062..5b79a6bd0ab 100644
--- a/pkg/front_end/testcases/extensions/instance_members.dart.strong.expect
+++ b/pkg/front_end/testcases/extensions/instance_members.dart.strong.expect
@@ -39,13 +39,13 @@ static method A2|method2<T extends core::Object* = dynamic>(final self::A1* #thi
 }
 static method A2|get#method2(final self::A1* #this) → <T extends core::Object* = dynamic>(T*) →* self::A1*
   return <T extends core::Object* = dynamic>(T* o) → self::A1* => self::A2|method2<T*>(#this, o);
-static method A2|method3<T extends core::Object* = dynamic>(final self::A1* #this = #C1, [self::A2|method3::T* o = #C1]) → self::A1* {
+static method A2|method3<T extends core::Object* = dynamic>(final self::A1* #this, [self::A2|method3::T* o = #C1]) → self::A1* {
   core::print(o);
   return #this;
 }
 static method A2|get#method3(final self::A1* #this) → <T extends core::Object* = dynamic>([T*]) →* self::A1*
   return <T extends core::Object* = dynamic>([T* o = #C1]) → self::A1* => self::A2|method3<T*>(#this, o);
-static method A2|method4<T extends core::Object* = dynamic>(final self::A1* #this = #C1, {self::A2|method4::T* o = #C1}) → self::A1* {
+static method A2|method4<T extends core::Object* = dynamic>(final self::A1* #this, {self::A2|method4::T* o = #C1}) → self::A1* {
   core::print(o);
   return #this;
 }
diff --git a/pkg/front_end/testcases/extensions/instance_members.dart.strong.transformed.expect b/pkg/front_end/testcases/extensions/instance_members.dart.strong.transformed.expect
index dfed3fb1062..5b79a6bd0ab 100644
--- a/pkg/front_end/testcases/extensions/instance_members.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/extensions/instance_members.dart.strong.transformed.expect
@@ -39,13 +39,13 @@ static method A2|method2<T extends core::Object* = dynamic>(final self::A1* #thi
 }
 static method A2|get#method2(final self::A1* #this) → <T extends core::Object* = dynamic>(T*) →* self::A1*
   return <T extends core::Object* = dynamic>(T* o) → self::A1* => self::A2|method2<T*>(#this, o);
-static method A2|method3<T extends core::Object* = dynamic>(final self::A1* #this = #C1, [self::A2|method3::T* o = #C1]) → self::A1* {
+static method A2|method3<T extends core::Object* = dynamic>(final self::A1* #this, [self::A2|method3::T* o = #C1]) → self::A1* {
   core::print(o);
   return #this;
 }
 static method A2|get#method3(final self::A1* #this) → <T extends core::Object* = dynamic>([T*]) →* self::A1*
   return <T extends core::Object* = dynamic>([T* o = #C1]) → self::A1* => self::A2|method3<T*>(#this, o);
-static method A2|method4<T extends core::Object* = dynamic>(final self::A1* #this = #C1, {self::A2|method4::T* o = #C1}) → self::A1* {
+static method A2|method4<T extends core::Object* = dynamic>(final self::A1* #this, {self::A2|method4::T* o = #C1}) → self::A1* {
   core::print(o);
   return #this;
 }
diff --git a/pkg/front_end/testcases/text_serialization.status b/pkg/front_end/testcases/text_serialization.status
index aba162c1933..95610cc1aa4 100644
--- a/pkg/front_end/testcases/text_serialization.status
+++ b/pkg/front_end/testcases/text_serialization.status
@@ -12,6 +12,7 @@ expression/main: TextSerializationFailure # Was: Pass
 extensions/annotations: TextSerializationFailure
 extensions/compounds: TextSerializationFailure
 extensions/conflicts: TextSerializationFailure
+extensions/default_values: TextSerializationFailure
 extensions/direct_instance_access: TextSerializationFailure
 extensions/direct_static_access: TextSerializationFailure
 extensions/dynamic_invoke: TextSerializationFailure
diff --git a/tests/modular/extension_methods/def.dart b/tests/modular/extension_methods/def.dart
index 665da3d8daa..d58df3b4864 100644
--- a/tests/modular/extension_methods/def.dart
+++ b/tests/modular/extension_methods/def.dart
@@ -11,6 +11,8 @@ class Class {
 extension Extension on Class {
   int method() => this.field;
 
+  int methodWithOptionals([int a = 42]) => a;
+
   int get property => this.field;
 
   void set property(int value) {
diff --git a/tests/modular/extension_methods/main.dart b/tests/modular/extension_methods/main.dart
index 760cc854466..cb1801852b1 100644
--- a/tests/modular/extension_methods/main.dart
+++ b/tests/modular/extension_methods/main.dart
@@ -24,10 +24,15 @@ testExplicitAccess(Class c) {
 
 testImplicitAccess(Class c) {
   Expect.equals(c.field, c.method());
+  Expect.equals(42, c.methodWithOptionals());
+  Expect.equals(123, c.methodWithOptionals(123));
   Expect.equals(c.field, c.property);
   Expect.equals(123, c.property = 123);
   var f = c.method;
   Expect.equals(c.field, f());
+  var f2 = c.methodWithOptionals;
+  Expect.equals(42, f2());
+  Expect.equals(87, f2(87));
 }
 
 testStaticAccess() {