diff --git a/shard.yml b/shard.yml
index 83320a1..230ddfc 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,8 +1,7 @@
 name: string_inflection
 version: 0.2.1
 
-crystal: 0.23.1
-
+crystal: '>= 0.23.1, < 2.0.0'
 authors:
   - mosop