diff --git a/usr.bin/ctags/C.c b/usr.bin/ctags/C.c
index ad7925428080..8d9e178cbd3b 100644
--- a/usr.bin/ctags/C.c
+++ b/usr.bin/ctags/C.c
@@ -42,6 +42,7 @@ __FBSDID("$FreeBSD$");
 
 #include <limits.h>
 #include <stdio.h>
+#include <string.h>
 
 #include "ctags.h"