2 files changed, 19 insertions, 4 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb b/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
index bc9b8dbfcf..28abdbd073 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/oid/uuid.rb
@@ -13,9 +13,12 @@ module ActiveRecord
             :uuid
           end
 
-          def cast(value)
-            value.to_s[ACCEPTABLE_UUID, 0]
-          end
+          private
+
+            def cast_value(value)
+              casted = value.to_s
+              casted if casted.match?(ACCEPTABLE_UUID)
+            end
         end
       end
     end
diff --git a/activerecord/test/cases/adapters/postgresql/uuid_test.rb b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
index 6591d50d06..d2d8ea8042 100644
--- a/activerecord/test/cases/adapters/postgresql/uuid_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
@@ -120,6 +120,16 @@ class PostgresqlUUIDTest < ActiveRecord::PostgreSQLTestCase
     assert_empty UUIDType.where(guid: "foobar")
   end
 
+  class DuckUUID
+    def initialize(uuid)
+      @uuid = uuid
+    end
+
+    def to_s
+      @uuid
+    end
+  end
+
   def test_acceptable_uuid_regex
     # Valid uuids
     ["A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11",
@@ -131,9 +141,11 @@ class PostgresqlUUIDTest < ActiveRecord::PostgreSQLTestCase
      # so we shouldn't block it either. (Pay attention to "fb6d" – the "f" here
      # is invalid – it must be one of 8, 9, A, B, a, b according to the spec.)
      "{a0eebc99-9c0b-4ef8-fb6d-6bb9bd380a11}",
+     # Support Object-Oriented UUIDs which respond to #to_s
+     DuckUUID.new("A0EEBC99-9C0B-4EF8-BB6D-6BB9BD380A11"),
     ].each do |valid_uuid|
       uuid = UUIDType.new guid: valid_uuid
-      assert_not_nil uuid.guid
+      assert_instance_of String, uuid.guid
     end
 
     # Invalid uuids