diff --git a/activesupport/lib/active_support/ordered_hash.rb b/activesupport/lib/active_support/ordered_hash.rb
index eda33f827ee26019493d2f00b62021bae5ae875d..b721e6f70a277bae2192830ed6ea11f4bffba019 100644
--- a/activesupport/lib/active_support/ordered_hash.rb
+++ b/activesupport/lib/active_support/ordered_hash.rb
@@ -131,7 +131,7 @@ def shift
 
       def merge!(other_hash)
         if block_given?
-          other_hash.each {|k,v| self[k] = yield(k, self[k], v) }
+          other_hash.each {|k,v| self[k] = yield(k, self[k], v) if key? k}
         else
           other_hash.each {|k,v| self[k] = v }
         end
diff --git a/activesupport/test/ordered_hash_test.rb b/activesupport/test/ordered_hash_test.rb
index 56369585ec30486ad41e94e4baccf438f8abcc57..e19484fb82a53a5092ae2e2192e188b1736749bb 100644
--- a/activesupport/test/ordered_hash_test.rb
+++ b/activesupport/test/ordered_hash_test.rb
@@ -144,28 +144,27 @@ def test_merge
   end
 
   def test_merge_with_block
-    other_hash = ActiveSupport::OrderedHash.new
-    other_hash['white'] = 'ff'
-    other_hash['black'] = '00'
-    merged = @ordered_hash.merge(other_hash) do |key, old_value, new_value|
-      new_value * 3
+    hash = ActiveSupport::OrderedHash.new
+    hash[:a] = 0
+    hash[:b] = 0
+    merged = hash.merge(:b => 1, :c => 2) do |key, old_value, new_value|
+      new_value + 1
     end
-    assert_equal 'ffffff', merged['white']
-    assert_equal '000000', merged['black']
-
-    assert_nil @ordered_hash['white']
-    assert_nil @ordered_hash['black']
+    assert_equal 0, merged[:a]
+    assert_equal 2, merged[:b]
+    assert !merged.key?(:c)
   end
 
   def test_merge_bang_with_block
-    other_hash = ActiveSupport::OrderedHash.new
-    other_hash['white'] = 'ff'
-    other_hash['black'] = '00'
-    @ordered_hash.merge!(other_hash) do |key, old_value, new_value|
-      new_value * 3
+    hash = ActiveSupport::OrderedHash.new
+    hash[:a] = 0
+    hash[:b] = 0
+    hash.merge!(:a => 1, :c => 2) do |key, old_value, new_value|
+      new_value + 3
     end
-    assert_equal 'ffffff', @ordered_hash['white']
-    assert_equal '000000', @ordered_hash['black']
+    assert_equal 4, hash[:a]
+    assert_equal 0, hash[:b]
+    assert !hash.key?(:c)
   end
 
   def test_shift