diff --git a/src/errorReporting/RuntimeTypeErrorItem.js.flow b/src/errorReporting/RuntimeTypeErrorItem.js.flow
index 6c971b9..79b88ac 100644
--- a/src/errorReporting/RuntimeTypeErrorItem.js.flow
+++ b/src/errorReporting/RuntimeTypeErrorItem.js.flow
@@ -16,4 +16,6 @@ declare export default class RuntimeTypeErrorItem {
     expectedTypeAtPath: Type<mixed>,
     depth?: number
   ): void;
+
+  messageAtPath(): string;
 }