diff --git a/ext/psych/lib/psych/versions.rb b/ext/psych/lib/psych/versions.rb
index 3cfd59e751..0a8632eefb 100644
--- a/ext/psych/lib/psych/versions.rb
+++ b/ext/psych/lib/psych/versions.rb
@@ -2,7 +2,7 @@
 
 module Psych
   # The version of Psych you are using
-  VERSION = '4.0.3'
+  VERSION = '4.0.4.dev'
 
   if RUBY_ENGINE == 'jruby'
     DEFAULT_SNAKEYAML_VERSION = '1.28'.freeze