diff --git a/mmh3module.cpp b/mmh3module.cpp
index 7bc7c02..2300b75 100644
--- a/mmh3module.cpp
+++ b/mmh3module.cpp
@@ -1,3 +1,4 @@
+#define PY_SSIZE_T_CLEAN
 #include <stdio.h>
 #include <string.h>
 #include <Python.h>