diff --git a/mozilla/gfx/src/nsDeviceContext.cpp b/mozilla/gfx/src/nsDeviceContext.cpp
index cac64e37813..aa379adf117 100644
--- a/mozilla/gfx/src/nsDeviceContext.cpp
+++ b/mozilla/gfx/src/nsDeviceContext.cpp
@@ -344,6 +344,11 @@ nsresult DeviceContextImpl::CreateIconILGroupContext()
 
 NS_IMETHODIMP DeviceContextImpl::LoadIconImage(PRInt32 aId, nsIImage*& aImage)
 {
+  // XXX synchronous image loading doesn't work on unix or mac yet
+  // because netlib is not in its own thread.
+#if defined(XP_UNIX) || defined(XP_MAC)
+  return NS_ERROR_FAILURE;
+#endif
   nsresult  result;
 
   // Initialize out parameter