1 files changed, 1 insertions, 0 deletions

diff --git a/class.c b/class.c
index 28d11dec49..6b1ccd22f7 100644
--- a/class.c
+++ b/class.c
@@ -13,6 +13,7 @@
 #include "ruby.h"
 #include "node.h"
 #include "st.h"
+#include <ctype.h>
 
 #ifdef USE_CWGUSI
 #include <stdio.h>