diff --git a/lib/class-factory.js b/lib/class-factory.js
index c066ad4c..f3b76f63 100644
--- a/lib/class-factory.js
+++ b/lib/class-factory.js
@@ -1647,6 +1647,12 @@ methodPrototype = Object.create(Function.prototype, {
         env.popLocalFrame(NULL);
       }
     }
+  },
+  toString: {
+    enumerable: true,
+    value () {
+      return `function ${this.methodName}(${this.argumentTypes.map(t => t.className).join(', ')}): ${this.returnType.className}`;
+    }
   }
 });