diff --git a/accessible/mac/mozHTMLAccessible.mm b/accessible/mac/mozHTMLAccessible.mm
index ca80cc1088c..4eddc00eaa4 100644
--- a/accessible/mac/mozHTMLAccessible.mm
+++ b/accessible/mac/mozHTMLAccessible.mm
@@ -17,7 +17,7 @@
 - (NSString*)title
 {
   nsAutoString title;
-  ErrorResult rv;
+  mozilla::ErrorResult rv;
   // XXX use the flattening API when there are available
   // see bug 768298
   mGeckoAccessible->GetContent()->GetTextContent(title, rv);