diff --git a/src/Combinators.mo b/src/Combinators.mo
index 5781dfb..68ca499 100644
--- a/src/Combinators.mo
+++ b/src/Combinators.mo
@@ -242,7 +242,7 @@ module {
             sat(func (x : Char) : Bool {
                 '0' <= x and x <= '9' or
                 'a' <= x and x <= 'f' or
-                'A' <= x and x <= 'A';
+                'A' <= x and x <= 'F';
             });
         };