diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 9579eae..71414c9 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -15,6 +15,7 @@
 */
 
 #include "Python.h"
+#include "internal/mem.h"
 #include "internal/pystate.h"
 #include "code.h"
 #include "frameobject.h"