diff --git a/layout/generic/nsFrame.cpp b/layout/generic/nsFrame.cpp
index 4355863e6bfd..325889e92ce5 100644
--- a/layout/generic/nsFrame.cpp
+++ b/layout/generic/nsFrame.cpp
@@ -8491,7 +8491,7 @@ static nsContentAndOffset FindLineBreakingFrame(nsIFrame* aFrame,
 
   // Treat form controls as inline leaves
   // XXX we really need a way to determine whether a frame is inline-level
-  if (nsIFormControlFrame* fcf = do_QueryFrame(aFrame)) {
+  if (static_cast<nsIFormControlFrame*>(do_QueryFrame(aFrame))) {
     return result;
   }