ensure freeze on Thread freezes locals

2 files changed, 14 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/core_ext/thread.rb b/activesupport/lib/active_support/core_ext/thread.rb
index 878ec73ef0..e80f442973 100644
--- a/activesupport/lib/active_support/core_ext/thread.rb
+++ b/activesupport/lib/active_support/core_ext/thread.rb
@@ -62,6 +62,11 @@ class Thread
     _locals.has_key?(key.to_sym)
   end
 
+  def freeze
+    _locals.freeze
+    super
+  end
+
   private
 
   def _locals
diff --git a/activesupport/test/core_ext/thread_test.rb b/activesupport/test/core_ext/thread_test.rb
index 230c1203ad..cf1b48d511 100644
--- a/activesupport/test/core_ext/thread_test.rb
+++ b/activesupport/test/core_ext/thread_test.rb
@@ -63,6 +63,15 @@ class ThreadExt < ActiveSupport::TestCase
     end
   end
 
+  def test_thread_variable_frozen_after_set
+    t = Thread.new { }.join
+    t.thread_variable_set :foo, "bar"
+    t.freeze
+    assert_raises(RuntimeError) do
+      t.thread_variable_set(:baz, "qux")
+    end
+  end
+
   def test_thread_variable_security
     t = Thread.new { sleep }