diff --git a/src/bin/unchop.c b/src/bin/unchop.c
index 93b214b037..548fbc6b68 100644
--- a/src/bin/unchop.c
+++ b/src/bin/unchop.c
@@ -14,6 +14,7 @@
 
 #include <OS.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include <fcntl.h>