diff --git a/json.gemspec b/json.gemspec
index c714ba86d..b97aece19 100644
--- a/json.gemspec
+++ b/json.gemspec
@@ -48,6 +48,7 @@ Gem::Specification.new do |s|
     "lib/json/add/struct.rb",
     "lib/json/add/symbol.rb",
     "lib/json/add/time.rb",
+    "lib/json/ext/generator/state.rb",
     "lib/json/common.rb",
     "lib/json/ext.rb",
     "lib/json/generic_object.rb",