diff --git a/runtime/bin/builtin.dart b/runtime/bin/builtin.dart
index 2fb0d5df777..e0108096f6c 100644
--- a/runtime/bin/builtin.dart
+++ b/runtime/bin/builtin.dart
@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 #library("builtin");
+#import("dart:uri");
 
 void print(arg) {
   _Logger._printString(arg.toString());
diff --git a/runtime/vm/class_finalizer.cc b/runtime/vm/class_finalizer.cc
index ceb4a7e2729..08641292961 100644
--- a/runtime/vm/class_finalizer.cc
+++ b/runtime/vm/class_finalizer.cc
@@ -1270,7 +1270,9 @@ void ClassFinalizer::FinalizeMalformedType(const Error& prev_error,
   va_list args;
   va_start(args, format);
   LanguageError& error = LanguageError::Handle();
-  if ((finalization == kFinalizeWellFormed) || FLAG_enable_type_checks) {
+  if (FLAG_enable_type_checks ||
+      !type.HasResolvedTypeClass() ||
+      (finalization == kFinalizeWellFormed)) {
     const Script& script = Script::Handle(cls.script());
     if (prev_error.IsNull()) {
       error ^= Parser::FormatError(
@@ -1283,12 +1285,15 @@ void ClassFinalizer::FinalizeMalformedType(const Error& prev_error,
       ReportError(error);
     }
   }
-  if (FLAG_enable_type_checks) {
-    // In checked mode, mark type as malformed.
+  if (FLAG_enable_type_checks || !type.HasResolvedTypeClass()) {
+    // In check mode, always mark the type as malformed.
+    // In production mode, mark the type as malformed only if its type class is
+    // not resolved.
     type.set_malformed_error(error);
   } else {
-     // In production mode, replace malformed type with Dynamic type.
-    type.set_type_class(Class::Handle(Object::dynamic_class()));
+     // In production mode, do not mark the type with a resolved type class as
+     // malformed, but make it raw.
+    ASSERT(type.HasResolvedTypeClass());
     type.set_arguments(AbstractTypeArguments::Handle());
   }
   if (!type.IsFinalized()) {
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 6151414449e..fbfb674587f 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -3166,11 +3166,16 @@ RawAbstractTypeArguments* Parser::ParseTypeArguments(
     do {
       ConsumeToken();
       type = ParseType(finalization);
-      types.Add(type);
       // Only keep the error for the first malformed type argument.
       if (malformed_error->IsNull() && type.IsMalformed()) {
         *malformed_error = type.malformed_error();
       }
+      // Map a malformed type argument to Dynamic, so that malformed types with
+      // a resolved type class are handled properly in production mode.
+      if (type.IsMalformed()) {
+        type = Type::DynamicType();
+      }
+      types.Add(type);
     } while (CurrentToken() == Token::kCOMMA);
     Token::Kind token = CurrentToken();
     if ((token == Token::kGT) || (token == Token::kSHR)) {
@@ -7217,7 +7222,9 @@ RawAbstractType* Parser::ParseType(
   }
   AbstractType& type = AbstractType::Handle(
       Type::New(type_class, type_arguments, type_name.ident_pos));
-  if (!malformed_error.IsNull()) {
+  // In production mode, malformed type arguments are mapped to Dynamic.
+  // In checked mode, a type with malformed type arguments is malformed.
+  if (FLAG_enable_type_checks && !malformed_error.IsNull()) {
     Type& parameterized_type = Type::Handle();
     parameterized_type ^= type.raw();
     parameterized_type.set_type_class(Class::Handle(Object::dynamic_class()));
diff --git a/tests/co19/co19-runtime.status b/tests/co19/co19-runtime.status
index d3fc315916a..359e80e8f05 100644
--- a/tests/co19/co19-runtime.status
+++ b/tests/co19/co19-runtime.status
@@ -205,7 +205,7 @@ Language/08_Interfaces/3_Factories_and_Constructors_A06_t07: Fail
 Language/08_Interfaces/3_Factories_and_Constructors_A06_t08: Fail
 Language/08_Interfaces/4_Superinterfaces/1_Inheritance_and_Overriding_A01_t02: Fail
 Language/08_Interfaces/4_Superinterfaces_A01_t02: Fail
-Language/09_Generics/09_Generics_A04_t06: Fail
+Language/09_Generics/09_Generics_A04_t06: Fail # Issue 439
 LibTest/core/FallThroughError/FallThroughError_A01_t01: Fail
 LibTest/core/FallThroughError/toString_A01_t01: Fail
 LibTest/core/Match/group_A01_t01: Fail # co19 issue 92
@@ -235,7 +235,7 @@ Language/11_Statements/11_Labels_A01_t03: Fail # TODO(vm-team): New failure at r
 Language/12_Libraries_and_Scripts/1_Imports_A05_t01: Fail # TODO(vm-team): New failure at r164. Please triage.
 
 [ $runtime == vm  && $unchecked ]
-Language/03_Overview/2_Privacy_A01_t06: Fail # TODO(vm-team): New failure at r164. Please triage.
+Language/09_Generics/09_Generics_A04_t04: Fail # co19 issue 117
 
 
 [ $runtime == vm && $arch == ia32 ]
diff --git a/tests/language/language-leg.status b/tests/language/language-leg.status
index 1633bc3d359..89503bb2673 100644
--- a/tests/language/language-leg.status
+++ b/tests/language/language-leg.status
@@ -61,6 +61,7 @@ GenericDeepTest: Fail # Expect.isTrue(false) fails.
 GenericInheritanceTest: Fail # Expect.isTrue(false) fails.
 GenericParameterizedExtendsTest: Fail # Expect.isTrue(false) fails.
 Instanceof2Test: Fail # Expect.equals(expected: <true>, actual: <false>) fails.
+Instanceof3Test: Fail # cannot resolve type UndeclaredType.
 LibraryPrivateInConstructorTest: Fail # Issue 2620.
 ListDoubleIndexInLoop2Test: Fail # Issue 2564.
 ListLiteral4Test: Fail # Illegal argument(s): 0 -- checked mode test.
diff --git a/tests/language/language.status b/tests/language/language.status
index eb191c7dcbd..14817799cab 100644
--- a/tests/language/language.status
+++ b/tests/language/language.status
@@ -73,7 +73,6 @@ ConstructorRedirectTest/01: Fail # Issue 2103.
 
 [ $compiler == none && $unchecked ]
 
-IsNotClass3NegativeTest: Fail  # Spec unclear.
 Prefix16NegativeTest: Fail    # Bug 5532534
 
 [ $compiler == none && $mode == debug ]
@@ -108,6 +107,7 @@ FunctionTypeAliasNegativeTest: Fail  # Bug 5231617.
 GenericParameterizedExtendsTest: Skip  # Bug 5392297
 GettersSettersType3Test: Fail # Issue 2351
 InstanceCallWrongArgumentCountNegativeTest: Fail
+Instanceof3Test: Fail # Issue 2571
 Label2NegativeTest: Fail    # issue 1658
 Library4NegativeTest: Fail   # Bug 5406175
 ListLiteral4Test: Fail       # Issue 1343
@@ -308,6 +308,7 @@ GetterClosureExecutionOrderTest: Pass # TODO(jmesserly): I don't think this is r
 ImplicitScopeTest: Fail
 ImpliedInterfaceTest: Fail
 Instanceof2Test: Fail
+Instanceof3Test: Fail # Issue 2571
 InterfaceFactory3NegativeTest: Fail
 IsNotClass4NegativeTest: Fail
 LabelTest: Fail
diff --git a/tests/language/src/Instanceof3Test.dart b/tests/language/src/Instanceof3Test.dart
new file mode 100644
index 00000000000..18006e2ff24
--- /dev/null
+++ b/tests/language/src/Instanceof3Test.dart
@@ -0,0 +1,86 @@
+// Copyright (c) 2012, 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.
+// Dart test program for testing the instanceof operation.
+
+// In the type test 'e is T', it is a run-time error if T does not denote a type
+// available in the current lexical scope.
+
+isCheckedMode() {
+  try {
+    var i = 1;
+    String s = i;
+    return false;
+  } catch(var e) {
+    return true;
+  }
+}
+
+main() {
+  {
+    bool got_type_error = false;
+    var x = null;
+    try {
+      Expect.isFalse(x is UndeclaredType);  // x is null.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in production mode and in checked mode.
+    Expect.isTrue(got_type_error);
+  }
+  {
+    bool got_type_error = false;
+    var x = 1;
+    try {
+      Expect.isFalse(x is UndeclaredType);  // x is not null.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in production mode and in checked mode.
+    Expect.isTrue(got_type_error);
+  }
+  {
+    bool got_type_error = false;
+    var x = null;
+    try {
+      Expect.isFalse(x is List<UndeclaredType>);  // x is null.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+  {
+    bool got_type_error = false;
+    var x = 1;
+    try {
+      Expect.isFalse(x is List<UndeclaredType>);  // x is not a List.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+  {
+    bool got_type_error = false;
+    var x = new List();
+    try {
+      Expect.isTrue(x is List<UndeclaredType>);  // x is a List<Dynamic>.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+  {
+    bool got_type_error = false;
+    var x = new List<int>();
+    try {
+      Expect.isTrue(x is List<UndeclaredType>);  // x is a List<int>.
+    } catch (TypeError error) {
+      got_type_error = true;
+    }
+    // Type error in checked mode only.
+    Expect.isTrue(got_type_error == isCheckedMode());
+  }
+}
diff --git a/tests/language/src/IsNotClass3NegativeTest.dart b/tests/language/src/IsNotClass3NegativeTest.dart
deleted file mode 100644
index 8b53ba68712..00000000000
--- a/tests/language/src/IsNotClass3NegativeTest.dart
+++ /dev/null
@@ -1,23 +0,0 @@
-// Copyright (c) 2011, 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.
-// Dart test program for catch that we expect a class after an 'is'.
-
-class A {
-  const A();
-}
-
-class IsNotClass3NegativeTest {
-  static testMain() {
-    var a = new A();
-
-    if (a is B) {
-      return 0;
-    }
-    return 0;
-  }
-}
-
-main() {
-  IsNotClass3NegativeTest.testMain();
-}