1 files changed, 8 insertions, 2 deletions
diff --git a/activesupport/lib/active_support/json/encoding.rb b/activesupport/lib/active_support/json/encoding.rb
index defaf3f395..de1b8ac8cf 100644
--- a/activesupport/lib/active_support/json/encoding.rb
+++ b/activesupport/lib/active_support/json/encoding.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require "active_support/core_ext/object/json"
 require "active_support/core_ext/module/delegation"
 
@@ -52,9 +54,13 @@ module ActiveSupport
           class EscapedString < String #:nodoc:
             def to_json(*)
               if Encoding.escape_html_entities_in_json
-                super.gsub ESCAPE_REGEX_WITH_HTML_ENTITIES, ESCAPED_CHARS
+                s = super
+                s.gsub! ESCAPE_REGEX_WITH_HTML_ENTITIES, ESCAPED_CHARS
+                s
               else
-                super.gsub ESCAPE_REGEX_WITHOUT_HTML_ENTITIES, ESCAPED_CHARS
+                s = super
+                s.gsub! ESCAPE_REGEX_WITHOUT_HTML_ENTITIES, ESCAPED_CHARS
+                s
               end
             end