diff --git a/activesupport/lib/active_support/core_ext/hash/keys.rb b/activesupport/lib/active_support/core_ext/hash/keys.rb
index ff8e68faa15cac91664ced06a9277326db1ead9d..7312bcb416c1801d71cea9670f9302f22f2ae28d 100644
--- a/activesupport/lib/active_support/core_ext/hash/keys.rb
+++ b/activesupport/lib/active_support/core_ext/hash/keys.rb
@@ -13,10 +13,7 @@ def stringify_keys
         # Destructively convert all keys to strings.
         def stringify_keys!
           keys.each do |key|
-            unless key.class.to_s == "String" # weird hack to make the tests run when string_ext_test.rb is also running
-              self[key.to_s] = self[key]
-              delete(key)
-            end
+            self[key.to_s] = delete(key)
           end
           self
         end