diff --git a/Include/Python.h b/Include/Python.h
index a5e2853..4cffda3 100644
--- a/Include/Python.h
+++ b/Include/Python.h
@@ -148,7 +148,7 @@
 #ifdef __CHAR_UNSIGNED__
 #define Py_CHARMASK(c)		(c)
 #else
-#define Py_CHARMASK(c)		((c) & 0xff)
+#define Py_CHARMASK(c)		((unsigned char)((c) & 0xff))
 #endif
 
 #include "pyfpe.h"