diff --git a/tools/tools/cxgbetool/cxgbetool.c b/tools/tools/cxgbetool/cxgbetool.c
index 39e737604dd..32f6d2694b8 100644
--- a/tools/tools/cxgbetool/cxgbetool.c
+++ b/tools/tools/cxgbetool/cxgbetool.c
@@ -31,6 +31,7 @@ __FBSDID("$FreeBSD$");
 #include <stdint.h>
 #include <stdlib.h>
 #include <unistd.h>
+#include <ctype.h>
 #include <errno.h>
 #include <err.h>
 #include <fcntl.h>