diff --git a/cbits/cryptonite_sysrand.c b/cbits/cryptonite_sysrand.c
index 05434ef..39a9c0c 100644
--- a/cbits/cryptonite_sysrand.c
+++ b/cbits/cryptonite_sysrand.c
@@ -28,6 +28,7 @@
  * SUCH DAMAGE.
  */
 
+#include <stdlib.h>
 #include <stdint.h>
 #include <sys/time.h>
 #include "cryptonite_sha512.h"