diff --git a/libass/ass_mp.c b/libass/ass_mp.c
index 34cc2946c3..8f0efd0bbf 100644
--- a/libass/ass_mp.c
+++ b/libass/ass_mp.c
@@ -1,5 +1,6 @@
 #include <inttypes.h>
 #include <string.h>
+#include <stdlib.h>
 
 #include "ass.h"
 #include "ass_mp.h"