1 files changed, 25 insertions, 0 deletions
diff --git a/activerecord/test/cases/relation/where_test.rb b/activerecord/test/cases/relation/where_test.rb
index d333be3560..3e460fa3d6 100644
--- a/activerecord/test/cases/relation/where_test.rb
+++ b/activerecord/test/cases/relation/where_test.rb
@@ -81,6 +81,31 @@ module ActiveRecord
       assert_equal expected.to_sql, actual.to_sql
     end
 
+    def test_decorated_polymorphic_where
+      treasure_decorator = Struct.new(:model) do
+        def self.method_missing(method, *args, &block)
+          Treasure.send(method, *args, &block)
+        end
+
+        def is_a?(klass)
+          model.is_a?(klass)
+        end
+
+        def method_missing(method, *args, &block)
+          model.send(method, *args, &block)
+        end
+      end
+
+      treasure = Treasure.new
+      treasure.id = 1
+      decorated_treasure = treasure_decorator.new(treasure)
+
+      expected = PriceEstimate.where(estimate_of_type: 'Treasure', estimate_of_id: 1)
+      actual   = PriceEstimate.where(estimate_of: decorated_treasure)
+
+      assert_equal expected.to_sql, actual.to_sql
+    end
+
     def test_aliased_attribute
       expected = Topic.where(heading: 'The First Topic')
       actual   = Topic.where(title: 'The First Topic')