diff --git a/shard.yml b/shard.yml
index 815d94a..af9e090 100644
--- a/shard.yml
+++ b/shard.yml
@@ -1,5 +1,5 @@
 name: kemal
-version: 0.20.0
+version: 0.21.0
 
 dependencies:
   radix:
diff --git a/src/kemal/dsl.cr b/src/kemal/dsl.cr
index c11733b..6dc9a53 100644
--- a/src/kemal/dsl.cr
+++ b/src/kemal/dsl.cr
@@ -14,7 +14,7 @@ FILTER_METHODS = %w(get post put patch delete options all)
   end
 {% end %}
 
-def ws(path : String, &block : HTTP::WebSocket, HTTP::Server::Context -> _)
+def ws(path : String, &block : HTTP::WebSocket, HTTP::Server::Context -> Void)
   raise Kemal::Exceptions::InvalidPathStartException.new("ws", path) unless Kemal::Utils.path_starts_with_slash?(path)
   Kemal::WebSocketHandler.new path, &block
 end