diff --git a/mypyc/lib-rt/CPy.h b/mypyc/lib-rt/CPy.h
index c0f998b15c42..c367efdae032 100644
--- a/mypyc/lib-rt/CPy.h
+++ b/mypyc/lib-rt/CPy.h
@@ -8,6 +8,7 @@
 #include <frameobject.h>
 #include <structmember.h>
 #include <assert.h>
+#include <stdint.h>
 #include "pythonsupport.h"
 #include "mypyc_util.h"