diff --git a/src/attrib.c b/src/attrib.c
index 0477b1196..e868edaf9 100644
--- a/src/attrib.c
+++ b/src/attrib.c
@@ -5,6 +5,7 @@
 /*  attribute modification routines. */
 
 #include "hack.h"
+#include <ctype.h>
 
 /* #define DEBUG */	/* uncomment for debugging info */