Do not cast value if it's already been casted.

lib/enumerize/activerecord.rb

@@ -126,13 +126,8 @@ def serialize(value)
       end
 
       def cast(value)
-        return value if @subtype.is_a?(Type)
-
-        if value.is_a?(::Enumerize::Value)
-          value
-        else
-          @attr.find_value(@subtype.cast(value))
-        end
+        value = @subtype.cast(value) if [email protected]_a?(Type) && !value.is_a?(Enumerize::Value)
+        @attr.find_value(value)
       end
 
       def as_json(options = nil)

test/activerecord_test.rb

@@ -731,6 +731,22 @@ class AdminUser < User
     expect(admin.account_type).must_equal 'pro'
   end
 
+  it 'has correct value in _was attribute' do
+    user = User.create(status: 'active')
+    user.status = 'blocked'
+    expect(user.status_was).must_equal 'active'
+  end
+
+  it 'has correct value in _was attribute in child class' do
+    class AdminUser < User
+      enumerize :status, :in => { active: 1, blocked: 2, inactive: 3 }, scope: true
+    end
+
+    admin = AdminUser.create(status: 'active')
+    admin.status = 'blocked'
+    expect(admin.status_was).must_equal 'active'
+  end
+
   if Rails::VERSION::MAJOR >= 6
     it 'supports AR#insert_all' do
       User.delete_all