diff --git a/pkg/analyzer_plugin/api.txt b/pkg/analyzer_plugin/api.txt
index e54d5aa329c..3a46c7c4e98 100644
--- a/pkg/analyzer_plugin/api.txt
+++ b/pkg/analyzer_plugin/api.txt
@@ -1682,8 +1682,7 @@ package:analyzer_plugin/utilities/assist/assist.dart:
     new (constructor: DartAssistRequest Function())
     result (getter: ResolvedUnitResult)
 package:analyzer_plugin/utilities/assist/assist_contributor_mixin.dart:
-  AssistContributorMixin (class extends Object implements AssistContributor):
-    new (constructor: AssistContributorMixin Function())
+  AssistContributorMixin (mixin on AssistContributor):
     collector (getter: AssistCollector)
     addAssist (method: void Function(AssistKind, ChangeBuilder, {List<Object>? args}))
 package:analyzer_plugin/utilities/change_builder/change_builder_core.dart:
diff --git a/pkg/analyzer_plugin/lib/utilities/assist/assist_contributor_mixin.dart b/pkg/analyzer_plugin/lib/utilities/assist/assist_contributor_mixin.dart
index 811a510e6e2..b61d7841554 100644
--- a/pkg/analyzer_plugin/lib/utilities/assist/assist_contributor_mixin.dart
+++ b/pkg/analyzer_plugin/lib/utilities/assist/assist_contributor_mixin.dart
@@ -12,7 +12,7 @@ import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dar
 ///
 /// Clients may not extend or implement this class, but are allowed to use it as
 /// a mix-in when creating a subclass of [AssistContributor].
-abstract class AssistContributorMixin implements AssistContributor {
+mixin AssistContributorMixin on AssistContributor {
   /// The collector to which assists should be added.
   AssistCollector get collector;