diff --git a/lang/m2/comp/defmodule.c b/lang/m2/comp/defmodule.c
index fc83d36fd..f26168a28 100644
--- a/lang/m2/comp/defmodule.c
+++ b/lang/m2/comp/defmodule.c
@@ -12,6 +12,7 @@
 #include "parameters.h"
 #include	"debug.h"
 
+#include <stdlib.h>
 #include	<assert.h>
 #include	<em_arith.h>
 #include	<em_label.h>