diff --git a/tools/mkzenboot.c b/tools/mkzenboot.c
index b345c0f5ac..e31bbd513c 100644
--- a/tools/mkzenboot.c
+++ b/tools/mkzenboot.c
@@ -24,6 +24,7 @@
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <stdbool.h>
 #include <inttypes.h>
 #include <zlib.h>