1 files changed, 10 insertions, 1 deletions
diff --git a/spec/ruby/core/string/insert_spec.rb b/spec/ruby/core/string/insert_spec.rb
index db42a37941..483f3c9367 100644
--- a/spec/ruby/core/string/insert_spec.rb
+++ b/spec/ruby/core/string/insert_spec.rb
@@ -1,5 +1,5 @@
 # -*- encoding: utf-8 -*-
-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -69,4 +69,13 @@ describe "String#insert with index, other" do
       "あれ".insert 0, pat
     end.should raise_error(Encoding::CompatibilityError)
   end
+
+  it "should not call subclassed string methods" do
+    cls = Class.new(String) do
+      def replace(arg)
+        raise "should not call replace"
+      end
+    end
+    cls.new("abcd").insert(0, 'X').should == "Xabcd"
+  end
 end