diff --git a/gfx/src/windows/nsFontMetricsWin.cpp b/gfx/src/windows/nsFontMetricsWin.cpp
index ebde03da986c..a7d4c154eb65 100644
--- a/gfx/src/windows/nsFontMetricsWin.cpp
+++ b/gfx/src/windows/nsFontMetricsWin.cpp
@@ -218,7 +218,7 @@ nsFontMetricsWin::RealizeFont()
   else
   {
     // Find font metrics and character widths
-    win = mDeviceContext->mWidget;
+    win = (HWND)mDeviceContext->mWidget;
     dc = ::GetDC(win);
   }