diff --git a/test/test_mutex_m.rb b/test/test_mutex_m.rb
index aba663d..5a2e5c3 100644
--- a/test/test_mutex_m.rb
+++ b/test/test_mutex_m.rb
@@ -119,4 +119,12 @@ def test_alias_included_class
     assert object.respond_to?(:try_lock)
     assert object.respond_to?(:synchronize)
   end
+
+  def test_try_lock_starts_unlocked
+    object = Object.new
+    object.extend(Mutex_m)
+
+    assert_equal true, object.try_lock
+    assert_equal false, object.try_lock
+  end
 end