Add uchar for NetBSD ctype.
diff --git a/src/libdraw/x11-init.c b/src/libdraw/x11-init.c
index 537920d..7229267 100644
--- a/src/libdraw/x11-init.c
+++ b/src/libdraw/x11-init.c
@@ -875,7 +875,7 @@
 	os = s;
 	*havemin = 0;
 	*r = Rect(0,0,0,0);
-	if(!isdigit(*s))
+	if(!isdigit((uchar)*s))
 		goto oops;
 	i = strtol(s, &s, 0);
 	if(*s == 'x'){