diff --git a/Include/mymath.h b/Include/mymath.h
index f4fffabf2f1..dd6ee58841d 100644
--- a/Include/mymath.h
+++ b/Include/mymath.h
@@ -11,7 +11,7 @@
 
 #ifndef HAVE_HYPOT
 extern double hypot Py_PROTO((double, double));
-#ifdef __MWERKS__
+#ifdef MWERKS_BEFORE_PRO4
 #define hypot we_dont_want_faulty_hypot_decl
 #endif
 #endif