diff --git a/mozilla/uriloader/exthandler/nsExternalHelperAppService.cpp b/mozilla/uriloader/exthandler/nsExternalHelperAppService.cpp
index db5a9fcf78d..2d687421558 100644
--- a/mozilla/uriloader/exthandler/nsExternalHelperAppService.cpp
+++ b/mozilla/uriloader/exthandler/nsExternalHelperAppService.cpp
@@ -1853,21 +1853,22 @@ NS_IMETHODIMP nsExternalHelperAppService::GetTypeFromURI(nsIURI *aURI, char **aC
 #ifdef XP_MAC
  	if (NS_SUCCEEDED(rv))
  	{
-    nsCAutoString fileExt;
-    url->GetFileExtension(fileExt);
-    
     nsresult rv2;
     nsCOMPtr<nsIFileURL> fileurl = do_QueryInterface( url, &rv2 );
     if ( NS_SUCCEEDED ( rv2 ) )
     {
-    	nsCOMPtr <nsIFile> file;
-    	rv2 = fileurl->GetFile( getter_AddRefs( file ) );
-    	if ( NS_SUCCEEDED( rv2 ) )
-    	{
-    		rv2 = GetTypeFromFile( file, aContentType );
-				if( NS_SUCCEEDED ( rv2 ) )
-					return rv2;
-			}			
+      PRBool isFileScheme = PR_FALSE;
+      if (NS_SUCCEEDED(fileurl->SchemeIs("file", &isFileScheme)) && isFileScheme)
+      {
+        nsCOMPtr <nsIFile> file;
+        rv2 = fileurl->GetFile(getter_AddRefs(file));
+        if (NS_SUCCEEDED(rv2))
+        {
+          rv2 = GetTypeFromFile(file, aContentType);
+          if (NS_SUCCEEDED(rv2))
+            return rv2;
+        }
+      }
     }
   }
 #endif