diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7438d5d86d98..980d2387bea1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2489,6 +2489,15 @@ breaking changes:
 
 #### `dart:developer`
 
+- **Breaking change** [#34233][]: The previously deprecated APIs
+  `kInvalidParams`, `kExtensionError`, `kExtensionErrorMax`, and
+  `kExtensionErrorMin` in [`ServiceExtensionResponse`][] have been removed. They
+  have been replaced by `invalidParams`, `extensionError`, `extensionErrorMax`,
+  and `extensionErrorMin`.
+
+[#34233]: https://github.com/dart-lang/sdk/issues/34233
+[`ServiceExtensionResponse`]: https://api.dart.dev/stable/dart-developer/ServiceExtensionResponse-class.html#constants
+
 - The constructors for `TimelineTask` now accept an optional `filterKey`
   parameter. If provided, the arguments for all events associated with the task
   will contain an entry named `filterKey`, set to the value of the `filterKey`
diff --git a/sdk/lib/_internal/vm/lib/developer.dart b/sdk/lib/_internal/vm/lib/developer.dart
index 46d050795d4f..3a78b32588d0 100644
--- a/sdk/lib/_internal/vm/lib/developer.dart
+++ b/sdk/lib/_internal/vm/lib/developer.dart
@@ -88,13 +88,13 @@ _runExtension(
   } catch (e, st) {
     var errorDetails = (st == null) ? '$e' : '$e\n$st';
     response = new ServiceExtensionResponse.error(
-        ServiceExtensionResponse.kExtensionError, errorDetails);
+        ServiceExtensionResponse.extensionError, errorDetails);
     _postResponse(replyPort, id, response, trace_service);
     return;
   }
   if (response is! Future) {
     response = new ServiceExtensionResponse.error(
-        ServiceExtensionResponse.kExtensionError,
+        ServiceExtensionResponse.extensionError,
         "Extension handler must return a Future");
     _postResponse(replyPort, id, response, trace_service);
     return;
@@ -103,13 +103,13 @@ _runExtension(
     // Catch any errors eagerly and wrap them in a ServiceExtensionResponse.
     var errorDetails = (st == null) ? '$e' : '$e\n$st';
     return new ServiceExtensionResponse.error(
-        ServiceExtensionResponse.kExtensionError, errorDetails);
+        ServiceExtensionResponse.extensionError, errorDetails);
   }).then((response) {
     // Post the valid response or the wrapped error after verifying that
     // the response is a ServiceExtensionResponse.
     if (response is! ServiceExtensionResponse) {
       response = new ServiceExtensionResponse.error(
-          ServiceExtensionResponse.kExtensionError,
+          ServiceExtensionResponse.extensionError,
           "Extension handler must complete to a ServiceExtensionResponse");
     }
     _postResponse(replyPort, id, response, trace_service);
diff --git a/sdk/lib/developer/extension.dart b/sdk/lib/developer/extension.dart
index aa106744ced0..ceef2d8ab8d9 100644
--- a/sdk/lib/developer/extension.dart
+++ b/sdk/lib/developer/extension.dart
@@ -45,22 +45,6 @@ class ServiceExtensionResponse {
     checkNotNullable(errorDetail, "errorDetail");
   }
 
-  /// Invalid method parameter(s) error code.
-  @deprecated
-  static const kInvalidParams = invalidParams;
-
-  /// Generic extension error code.
-  @deprecated
-  static const kExtensionError = extensionError;
-
-  /// Maximum extension provided error code.
-  @deprecated
-  static const kExtensionErrorMax = extensionErrorMax;
-
-  /// Minimum extension provided error code.
-  @deprecated
-  static const kExtensionErrorMin = extensionErrorMin;
-
   /// Invalid method parameter(s) error code.
   static const invalidParams = -32602;
 
diff --git a/tests/lib/fix_data_tests/developer.dart b/tests/lib/fix_data_tests/developer.dart
index a9dc42b180ae..6f4d9d59d9be 100644
--- a/tests/lib/fix_data_tests/developer.dart
+++ b/tests/lib/fix_data_tests/developer.dart
@@ -5,8 +5,8 @@
 import 'dart:developer';
 
 void main() {
-  print(ServiceExtensionResponse.kInvalidParams);
-  print(ServiceExtensionResponse.kExtensionError);
-  print(ServiceExtensionResponse.kExtensionErrorMax);
-  print(ServiceExtensionResponse.kExtensionErrorMin);
+  print(ServiceExtensionResponse.invalidParams);
+  print(ServiceExtensionResponse.extensionError);
+  print(ServiceExtensionResponse.extensionErrorMax);
+  print(ServiceExtensionResponse.extensionErrorMin);
 }