diff --git a/core/AmZRTP.cpp b/core/AmZRTP.cpp
index cb4df72b..d346ff67 100644
--- a/core/AmZRTP.cpp
+++ b/core/AmZRTP.cpp
@@ -33,6 +33,7 @@
 #include "log.h"
 #include "AmConfigReader.h"
 #include "AmUtils.h"
+#include <stdlib.h>
 
 #define ZRTP_CACHE_SAVE_INTERVAL 1