diff --git a/Modules/_ctypes/callproc.c b/Modules/_ctypes/callproc.c
index f5d8f52e3f9..d0693b6c7d7 100644
--- a/Modules/_ctypes/callproc.c
+++ b/Modules/_ctypes/callproc.c
@@ -70,6 +70,7 @@
 
 #include <ffi.h>
 #include "ctypes.h"
+#include <alloca.h>
 
 #if defined(_DEBUG) || defined(__MINGW32__)
 /* Don't use structured exception handling on Windows if this is defined.