1 files changed, 1 insertions, 0 deletions

diff --git a/numeric.c b/numeric.c
index 763e4d2ba6..1c89e11806 100644
--- a/numeric.c
+++ b/numeric.c
@@ -12,6 +12,7 @@
 
 #include "ruby.h"
 #include "env.h"
+#include <ctype.h>
 #include <math.h>
 #include <stdio.h>