diff --git a/src/pyi2c.c b/src/pyi2c.c
index e5b03ea..54babc8 100644
--- a/src/pyi2c.c
+++ b/src/pyi2c.c
@@ -1,3 +1,4 @@
+#define PY_SSIZE_T_CLEAN 1
 #include <Python.h>
 #include "i2c/i2c.h"