--- a/content/base/src/nsImageLoadingContent.cpp
+++ b/content/base/src/nsImageLoadingContent.cpp
@@ -42,17 +42,17 @@
 #include "nsIContentPolicy.h"
 #include "nsSVGEffects.h"
 
 #include "mozAutoDocUpdate.h"
 #include "mozilla/AsyncEventDispatcher.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/ScriptSettings.h"
 
-#if defined(XP_WIN)
+#ifdef LoadImage
 // Undefine LoadImage to prevent naming conflict with Windows.
 #undef LoadImage
 #endif
 
 using namespace mozilla;
 
 #ifdef DEBUG_chb
 static void PrintReqURL(imgIRequest* req) {

--- a/content/base/src/nsImageLoadingContent.h
+++ b/content/base/src/nsImageLoadingContent.h
@@ -26,16 +26,21 @@
 class nsIURI;
 class nsIDocument;
 class imgILoader;
 class nsIIOService;
 class nsPresContext;
 class nsIContent;
 class imgRequestProxy;
 
+#ifdef LoadImage
+// Undefine LoadImage to prevent naming conflict with Windows.
+#undef LoadImage
+#endif
+
 class nsImageLoadingContent : public nsIImageLoadingContent,
                               public imgIOnloadBlocker
 {
   /* METHODS */
 public:
   nsImageLoadingContent();
   virtual ~nsImageLoadingContent();