1 files changed, 5 insertions, 4 deletions
diff --git a/activesupport/lib/active_support/core_ext/hash/deep_merge.rb b/activesupport/lib/active_support/core_ext/hash/deep_merge.rb
index ffde34a741..24d0a2a481 100644
--- a/activesupport/lib/active_support/core_ext/hash/deep_merge.rb
+++ b/activesupport/lib/active_support/core_ext/hash/deep_merge.rb
@@ -1,11 +1,12 @@
 class Hash
   # Returns a new hash with +self+ and +other_hash+ merged recursively.
   def deep_merge(other_hash)
-    merge(other_hash) do |key, oldval, newval|
-      oldval = oldval.to_hash if oldval.respond_to?(:to_hash)
-      newval = newval.to_hash if newval.respond_to?(:to_hash)
-      oldval.is_a?( Hash ) && newval.is_a?( Hash ) ? oldval.deep_merge(newval) : newval
+    target = dup
+    other_hash.each_pair do |k,v|
+      tv = target[k]
+      target[k] = tv.is_a?(Hash) && v.is_a?(Hash) ? tv.deep_merge(v) : v
     end
+    target
   end
 
   # Returns a new hash with +self+ and +other_hash+ merged recursively.