diff --git a/content/base/src/nsDOMFileReader.cpp b/content/base/src/nsDOMFileReader.cpp
index 502e1d1ccb1..dca4aca1412 100644
--- a/content/base/src/nsDOMFileReader.cpp
+++ b/content/base/src/nsDOMFileReader.cpp
@@ -242,6 +242,9 @@ nsDOMFileReader::GetResult(JSContext* aCx, jsval* aResult)
     } else {
       *aResult = JSVAL_NULL;
     }
+    if (!JS_WrapValue(aCx, aResult)) {
+      return NS_ERROR_FAILURE;
+    }
     return NS_OK;
   }