diff --git a/Python/thread.c b/Python/thread.c
index 0f46223..fcaa10d 100644
--- a/Python/thread.c
+++ b/Python/thread.c
@@ -88,6 +88,10 @@
 #define SUN_LWP
 #endif
 
+#ifdef __MWERKS__
+#define _POSIX_THREADS
+#endif
+
 #endif /* _POSIX_THREADS */
 
 #ifdef __STDC__