diff --git a/Lib/plat-mac/macresource.py b/Lib/plat-mac/macresource.py
index 52e3e89..bb9e2d9 100644
--- a/Lib/plat-mac/macresource.py
+++ b/Lib/plat-mac/macresource.py
@@ -107,7 +107,7 @@
         refno = Res.FSpOpenResFile(pathname, 1)
         Res.CloseResFile(refno)
     except (AttributeError, Res.Error), arg:
-        if instance(arg, AttributeError), or arg[0] in (-37, -39):
+        if isinstance(arg, AttributeError) or arg[0] in (-37, -39):
             # No resource fork. We may be on OSX, and this may be either
             # a data-fork based resource file or a AppleSingle file
             # from the CVS repository.