diff --git a/src/cndm/modules/cndm/cndm_cmd.c b/src/cndm/modules/cndm/cndm_cmd.c
index 6ff1ad9..859de1d 100644
--- a/src/cndm/modules/cndm/cndm_cmd.c
+++ b/src/cndm/modules/cndm/cndm_cmd.c
@@ -10,6 +10,8 @@ Authors:
 
 #include "cndm.h"
 
+#include <linux/ctype.h>
+
 int cndm_exec_mbox_cmd(struct cndm_dev *cdev, void *cmd, void *rsp)
 {
 	bool done = false;