diff --git a/src/dfa.c b/src/dfa.c
index 3122e22..c88235c 100644
--- a/src/dfa.c
+++ b/src/dfa.c
@@ -469,6 +469,8 @@ static int
 in_coll_range (char ch, char from, char to)
 {
   char c[6] = { from, 0, ch, 0, to, 0 };
+  if (ch < 128)
+    return from <= ch && ch <= to;
   return strcoll (&c[0], &c[2]) <= 0 && 0 <= strcoll (&c[2], &c[4]);
 }
