diff --git a/lib/webmock/response.rb b/lib/webmock/response.rb
index e09eb608..5456f5a7 100644
--- a/lib/webmock/response.rb
+++ b/lib/webmock/response.rb
@@ -38,7 +38,7 @@ def headers=(headers)
     end
 
     def body
-      @body || ''
+      @body || String.new
     end
 
     def body=(body)
diff --git a/spec/unit/response_spec.rb b/spec/unit/response_spec.rb
index 168e64cd..5707000e 100644
--- a/spec/unit/response_spec.rb
+++ b/spec/unit/response_spec.rb
@@ -101,6 +101,10 @@
       expect(@response.body).to eq('')
     end
 
+    it "should return unfrozen string empty body by default" do
+      expect(@response.body).to_not be_frozen
+    end
+
     it "should report body if assigned" do
       @response = WebMock::Response.new(body: "abc")
       expect(@response.body).to eq("abc")