Use #if TARGET_API_MAC_CARBON to determine carbon/classic macos, not #ifdef.
diff --git a/Python/dynload_mac.c b/Python/dynload_mac.c
index e5e08e3..c8c9646 100644
--- a/Python/dynload_mac.c
+++ b/Python/dynload_mac.c
@@ -20,7 +20,7 @@
 #ifdef __CFM68K__
 	{".CFM68K.slb", "rb", C_EXTENSION},
 #else
-#ifdef TARGET_API_MAC_CARBON
+#if TARGET_API_MAC_CARBON
 	{".carbon.slb", "rb", C_EXTENSION},
 #else
 	{".ppc.slb", "rb", C_EXTENSION},