diff --git a/src/dskread.c b/src/dskread.c
index 96729a0..fe132d1 100755
--- a/src/dskread.c
+++ b/src/dskread.c
@@ -1,3 +1,4 @@
+#include <ctype.h>
 #include "a2lib.c"
 
 char online[] = {