diff --git a/mediapipe/web/graph_runner/graph_runner.ts b/mediapipe/web/graph_runner/graph_runner.ts
index 795cd4061..4417f6a03 100644
--- a/mediapipe/web/graph_runner/graph_runner.ts
+++ b/mediapipe/web/graph_runner/graph_runner.ts
@@ -1123,6 +1123,18 @@ async function runScript(scriptUrl: string) {
   }
 }
 
+/**
+ * Helper type macro for use with createMediaPipeLib. Allows us to easily infer
+ * the type of a mixin-extended GraphRunner. Example usage:
+ * const GraphRunnerConstructor =
+ *     SupportImage(SupportSerialization(GraphRunner));
+ * let mediaPipe: ReturnType<typeof GraphRunnerConstructor>;
+ * ...
+ * mediaPipe = await createMediaPipeLib(GraphRunnerConstructor, ...);
+ */
+// tslint:disable-next-line:no-any
+export type ReturnType<T> = T extends (...args: unknown[]) => infer R ? R : any;
+
 /**
  * Global function to initialize Wasm blob and load runtime assets for a
  *     specialized MediaPipe library. This allows us to create a requested