Be less harsh on serializers.

lib/devise/serializers/base.rb

@@ -12,21 +12,8 @@ module Devise
         mapping.to.send(:"serialize_from_#{serialization_type}", keys)
       end
 
-      def store(user, scope)
-        @scope = scope
-        return unless valid?
-        super
-      end
-
       def fetch(scope)
         @scope = scope
-        return unless valid?
-        super
-      end
-
-      def delete(scope, user=nil)
-        @scope = scope
-        return unless valid?
         super
       end
 
@@ -38,4 +25,4 @@ module Devise
       end
     end
   end
-end
+end

lib/devise/serializers/rememberable.rb

@@ -10,17 +10,19 @@ module Devise
           super
         end
       end
-      
+
       def default_options(record)
         super.merge!(:expires => record.remember_expires_at)
       end
 
       def delete(scope, record=nil)
-        record.forget_me! if record && record.respond_to?(:forget_me!)
-        super
+        if record && record.respond_to?(:forget_me!)
+          record.forget_me!
+          super
+        end
       end
     end
   end
 end
 
-Warden::Serializers.add(:rememberable, Devise::Serializers::Rememberable)
+Warden::Serializers.add(:rememberable, Devise::Serializers::Rememberable)