1 files changed, 12 insertions, 0 deletions
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index ab14a3c17b..4add7dfe2f 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -887,6 +887,18 @@ CODE
     end
   end
 
+  class StringWithIVSet < String
+    def set_iv
+      @foo = 1
+    end
+  end
+
+  def test_ivar_set_after_frozen_dup
+    str = StringWithIVSet.new.freeze
+    str.dup.set_iv
+    assert_raise(FrozenError) { str.set_iv }
+  end
+
   def test_each
     verbose, $VERBOSE = $VERBOSE, nil