diff --git a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
index 8ebf870b95f8b..a4866f5a8facb 100644
--- a/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
+++ b/actionpack/lib/action_dispatch/middleware/session/cookie_store.rb
@@ -59,7 +59,8 @@ def unpacked_cookie_data(env)
       end
 
       def set_session(env, sid, session_data, options)
-        session_data.merge("session_id" => sid)
+        session_data["session_id"] = sid
+        session_data
       end
 
       def set_cookie(env, session_id, cookie)
diff --git a/actionpack/test/template/form_helper_test.rb b/actionpack/test/template/form_helper_test.rb
index 3b1af47770b6a..c5a32635f86fd 100644
--- a/actionpack/test/template/form_helper_test.rb
+++ b/actionpack/test/template/form_helper_test.rb
@@ -2238,7 +2238,7 @@ def initialize(object_name, object, template, options, block)
       end
     end
 
-    assert_deprecated /Giving a block to FormBuilder is deprecated and has no effect anymore/ do
+    assert_deprecated(/Giving a block to FormBuilder is deprecated and has no effect anymore/) do
       builder_class.new(:foo, nil, nil, {}, proc {})
     end
   end