diff --git a/pkg/dart2bytecode/docs/bytecode.md b/pkg/dart2bytecode/docs/bytecode.md
index 97634cf6189..5bb89d4e215 100644
--- a/pkg/dart2bytecode/docs/bytecode.md
+++ b/pkg/dart2bytecode/docs/bytecode.md
@@ -524,7 +524,7 @@ type FieldDeclaration {
                 hasGetter, hasSetter,
                 hasInitializer, hasNontrivialInitializer, hasInitializerCode,
                 hasSourcePositions, hasAnnotations, hasPragma,
-                hasCustomScript);
+                hasCustomScript, isExtensionTypeMember);
   PackedObject name;
   PackedObject type;
 
@@ -557,7 +557,7 @@ type FunctionDeclaration {
                 isAsync, isAsyncStar, isSyncStar,
                 isNoSuchMethodForwarder, isExternal, isNative,
                 hasSourcePositions, hasAnnotations, hasPragma,
-                hasCustomScript);
+                hasCustomScript, isExtensionTypeMember);
 
   PackedObject name;
 
diff --git a/pkg/dart2bytecode/lib/bytecode_generator.dart b/pkg/dart2bytecode/lib/bytecode_generator.dart
index 1199dcc96c3..ec88f4ae917 100644
--- a/pkg/dart2bytecode/lib/bytecode_generator.dart
+++ b/pkg/dart2bytecode/lib/bytecode_generator.dart
@@ -502,6 +502,9 @@ class BytecodeGenerator extends RecursiveVisitor {
     if (field.isExtensionMember) {
       flags |= FieldDeclaration.isExtensionMemberFlag;
     }
+    if (field.isExtensionTypeMember) {
+      flags |= FieldDeclaration.isExtensionTypeMemberFlag;
+    }
     // In NNBD libraries, static fields with initializers are implicitly late.
     if (field.isLate || (field.isStatic && field.initializer != null)) {
       flags |= FieldDeclaration.isLateFlag;
@@ -569,6 +572,9 @@ class BytecodeGenerator extends RecursiveVisitor {
     if (member.isExtensionMember) {
       flags |= FunctionDeclaration.isExtensionMemberFlag;
     }
+    if (member.isExtensionTypeMember) {
+      flags |= FunctionDeclaration.isExtensionTypeMemberFlag;
+    }
 
     FunctionNode function = member.function!;
     if (function.requiredParameterCount !=
diff --git a/pkg/dart2bytecode/lib/declarations.dart b/pkg/dart2bytecode/lib/declarations.dart
index 07b5b57605d..1f72bcf91a0 100644
--- a/pkg/dart2bytecode/lib/declarations.dart
+++ b/pkg/dart2bytecode/lib/declarations.dart
@@ -360,6 +360,7 @@ class FieldDeclaration {
   static const hasAnnotationsFlag = 1 << 14;
   static const hasPragmaFlag = 1 << 15;
   static const hasCustomScriptFlag = 1 << 16;
+  static const isExtensionTypeMemberFlag = 1 << 17;
 
   final int flags;
   final ObjectHandle name;
@@ -475,6 +476,9 @@ class FieldDeclaration {
     if ((flags & isExtensionMemberFlag) != 0) {
       sb.write(', extension-member');
     }
+    if ((flags & isExtensionTypeMemberFlag) != 0) {
+      sb.write(', extension-type-member');
+    }
     if ((flags & hasPragmaFlag) != 0) {
       sb.write(', has-pragma');
     }
@@ -526,6 +530,7 @@ class FunctionDeclaration {
   static const hasAnnotationsFlag = 1 << 21;
   static const hasPragmaFlag = 1 << 22;
   static const hasCustomScriptFlag = 1 << 23;
+  static const isExtensionTypeMemberFlag = 1 << 24;
 
   final int flags;
   final ObjectHandle name;
@@ -678,6 +683,9 @@ class FunctionDeclaration {
     if ((flags & isExtensionMemberFlag) != 0) {
       sb.write(', extension-member');
     }
+    if ((flags & isExtensionTypeMemberFlag) != 0) {
+      sb.write(', extension-type-member');
+    }
     if ((flags & hasOptionalPositionalParamsFlag) != 0) {
       sb.write(', has-optional-positional-params');
     }
diff --git a/runtime/vm/bytecode_reader.cc b/runtime/vm/bytecode_reader.cc
index ba70b736c65..14fce3c5a78 100644
--- a/runtime/vm/bytecode_reader.cc
+++ b/runtime/vm/bytecode_reader.cc
@@ -1782,6 +1782,7 @@ void BytecodeReaderHelper::ReadFieldDeclarations(const Class& cls,
   const int kHasAnnotationsFlag = 1 << 14;
   const int kHasPragmaFlag = 1 << 15;
   const int kHasCustomScriptFlag = 1 << 16;
+  const int kIsExtensionTypeMemberFlag = 1 << 17;
 
   const int num_fields = reader_.ReadListLength();
   if ((num_fields == 0) && !cls.is_enum_class()) {
@@ -1807,6 +1808,8 @@ void BytecodeReaderHelper::ReadFieldDeclarations(const Class& cls,
         (flags & kHasNontrivialInitializerFlag) != 0;
     const bool has_pragma = (flags & kHasPragmaFlag) != 0;
     const bool is_extension_member = (flags & kIsExtensionMemberFlag) != 0;
+    const bool is_extension_type_member =
+        (flags & kIsExtensionTypeMemberFlag) != 0;
     const bool has_initializer = (flags & kHasInitializerFlag) != 0;
 
     name ^= ReadObject();
@@ -1836,6 +1839,7 @@ void BytecodeReaderHelper::ReadFieldDeclarations(const Class& cls,
     field.set_is_generic_covariant_impl((flags & kIsCovariantByClassFlag) != 0);
     field.set_has_nontrivial_initializer(has_nontrivial_initializer);
     field.set_is_extension_member(is_extension_member);
+    field.set_is_extension_type_member(is_extension_type_member);
     field.set_has_initializer(has_initializer);
 
     if (!has_nontrivial_initializer) {
@@ -1881,6 +1885,7 @@ void BytecodeReaderHelper::ReadFieldDeclarations(const Class& cls,
       function.set_is_debuggable(false);
       function.set_accessor_field(field);
       function.set_is_extension_member(is_extension_member);
+      function.set_is_extension_type_member(is_extension_type_member);
       SetupFieldAccessorFunction(cls, function, type);
       if (is_static) {
         function.AttachBytecode(Object::implicit_static_getter_bytecode());
@@ -1907,6 +1912,7 @@ void BytecodeReaderHelper::ReadFieldDeclarations(const Class& cls,
       function.set_is_debuggable(false);
       function.set_accessor_field(field);
       function.set_is_extension_member(is_extension_member);
+      function.set_is_extension_type_member(is_extension_type_member);
       SetupFieldAccessorFunction(cls, function, type);
       if (is_static) {
         function.AttachBytecode(Object::implicit_static_setter_bytecode());
@@ -2032,6 +2038,7 @@ void BytecodeReaderHelper::ReadFunctionDeclarations(const Class& cls) {
   const int kHasAnnotationsFlag = 1 << 21;
   const int kHasPragmaFlag = 1 << 22;
   const int kHasCustomScriptFlag = 1 << 23;
+  const int kIsExtensionTypeMemberFlag = 1 << 24;
 
   const intptr_t num_functions = reader_.ReadListLength();
   ASSERT(function_index_ + num_functions == functions_->Length());
@@ -2057,6 +2064,8 @@ void BytecodeReaderHelper::ReadFunctionDeclarations(const Class& cls) {
     const bool is_native = (flags & kIsNativeFlag) != 0;
     const bool has_pragma = (flags & kHasPragmaFlag) != 0;
     const bool is_extension_member = (flags & kIsExtensionMemberFlag) != 0;
+    const bool is_extension_type_member =
+        (flags & kIsExtensionTypeMemberFlag) != 0;
 
     name ^= ReadObject();
 
@@ -2106,6 +2115,7 @@ void BytecodeReaderHelper::ReadFunctionDeclarations(const Class& cls) {
     function.set_is_reflectable((flags & kIsReflectableFlag) != 0);
     function.set_is_debuggable((flags & kIsDebuggableFlag) != 0);
     function.set_is_extension_member(is_extension_member);
+    function.set_is_extension_type_member(is_extension_type_member);
 
     if ((flags & kIsSyncStarFlag) != 0) {
       function.set_modifier(UntaggedFunction::kSyncGen);