--- a/utils/libcecutil/cec-info.cpp
+++ b/utils/libcecutil/cec-info.cpp
@@ -5,6 +5,7 @@
  * Copyright 2017 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
  */
 
+#include <cctype>
 #include <stdio.h>
 #include <string>
 #include <unistd.h>