Fixed compile error on windows.
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 503a611..0d6aa4a 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -740,7 +740,7 @@
 	}
 
 	/* Check the format_spec type, and make sure it's str or unicode */
-#if Py_USING_UNICODE
+#ifdef Py_USING_UNICODE
 	if (PyUnicode_Check(format_spec))
 		spec_is_unicode = 1;
 	else if (PyString_Check(format_spec))