diff --git a/pkg/front_end/lib/src/source/source_loader.dart b/pkg/front_end/lib/src/source/source_loader.dart
index 5b644013dba..946cd79fa72 100644
--- a/pkg/front_end/lib/src/source/source_loader.dart
+++ b/pkg/front_end/lib/src/source/source_loader.dart
@@ -2948,6 +2948,13 @@ severity: $severity
       if (redirectingFactoryBuilders != null) {
         for (RedirectingFactoryBuilder redirectingFactoryBuilder
             in redirectingFactoryBuilders) {
+          if (redirectingFactoryBuilder.parent.isExtension) {
+            // Extensions don't build their redirecting factories so we can't
+            // process them. Once they are added in
+            // [DeclarationNameSpaceBuilder.buildNameSpace] this skipping can
+            // likely be removed.
+            continue;
+          }
           redirectingFactoryBuilder.buildOutlineExpressions(
               classHierarchy, delayedDefaultValueCloners);
         }
diff --git a/pkg/front_end/lib/src/source/type_parameter_scope_builder.dart b/pkg/front_end/lib/src/source/type_parameter_scope_builder.dart
index aa32e32a087..bb98b9f499e 100644
--- a/pkg/front_end/lib/src/source/type_parameter_scope_builder.dart
+++ b/pkg/front_end/lib/src/source/type_parameter_scope_builder.dart
@@ -1459,6 +1459,10 @@ class DeclarationNameSpaceBuilder {
         // TODO(johnniwinther): Handle constructors in extensions consistently.
         // Currently they are not part of the name space but still processed
         // for instance when inferring redirecting factories.
+        // They are part of the name space for extension types though.
+        // Note that we have to remove [RedirectingFactoryBuilder]s in
+        // [SourceLoader.inferRedirectingFactories] as we don't build them
+        // because we don't add them here.
         constructors: includeConstructors ? constructors : null);
   }
 }
diff --git a/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart
new file mode 100644
index 00000000000..12cd3816df2
--- /dev/null
+++ b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart
@@ -0,0 +1,7 @@
+// Copyright (c) 2024, 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.
+
+extension Foo on String {
+  factory Foo({ this.fooX }) = Foobar;
+}
diff --git a/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.expect b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.expect
new file mode 100644
index 00000000000..c426da08db2
--- /dev/null
+++ b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.expect
@@ -0,0 +1,14 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart:6:3: Error: Extensions can't declare constructors.
+// Try removing the constructor declaration.
+//   factory Foo({ this.fooX }) = Foobar;
+//   ^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+extension Foo on core::String {
+}
diff --git a/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.modular.expect b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.modular.expect
new file mode 100644
index 00000000000..c426da08db2
--- /dev/null
+++ b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.modular.expect
@@ -0,0 +1,14 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart:6:3: Error: Extensions can't declare constructors.
+// Try removing the constructor declaration.
+//   factory Foo({ this.fooX }) = Foobar;
+//   ^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+extension Foo on core::String {
+}
diff --git a/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.outline.expect b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.outline.expect
new file mode 100644
index 00000000000..c426da08db2
--- /dev/null
+++ b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.outline.expect
@@ -0,0 +1,14 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart:6:3: Error: Extensions can't declare constructors.
+// Try removing the constructor declaration.
+//   factory Foo({ this.fooX }) = Foobar;
+//   ^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+extension Foo on core::String {
+}
diff --git a/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.transformed.expect b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.transformed.expect
new file mode 100644
index 00000000000..c426da08db2
--- /dev/null
+++ b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.strong.transformed.expect
@@ -0,0 +1,14 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart:6:3: Error: Extensions can't declare constructors.
+// Try removing the constructor declaration.
+//   factory Foo({ this.fooX }) = Foobar;
+//   ^^^^^^^
+//
+import self as self;
+import "dart:core" as core;
+
+extension Foo on core::String {
+}
diff --git a/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.textual_outline.expect b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.textual_outline.expect
new file mode 100644
index 00000000000..fe43f4db413
--- /dev/null
+++ b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.textual_outline.expect
@@ -0,0 +1,3 @@
+extension Foo on String {
+  factory Foo({ this.fooX }) = Foobar;
+}
diff --git a/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..fe43f4db413
--- /dev/null
+++ b/pkg/front_end/testcases/regress/extension_with_redirecting_factory.dart.textual_outline_modelled.expect
@@ -0,0 +1,3 @@
+extension Foo on String {
+  factory Foo({ this.fooX }) = Foobar;
+}