diff --git a/lib/bullet/detector/n_plus_one_query.rb b/lib/bullet/detector/n_plus_one_query.rb
index 650ea3c9..4b27d4ef 100644
--- a/lib/bullet/detector/n_plus_one_query.rb
+++ b/lib/bullet/detector/n_plus_one_query.rb
@@ -48,6 +48,7 @@ def add_possible_objects(object_or_objects)
             end
             obj.bullet_key
           end.join(", ")
+
           unless class_names_match_regex || primary_key_values_are_empty
             Bullet.debug('Detector::NPlusOneQuery#add_possible_objects', "objects: #{keys_joined}")
             objects.each { |object| possible_objects.add object.bullet_key }
diff --git a/lib/bullet/ext/string.rb b/lib/bullet/ext/string.rb
index ed4ee285..8319d537 100644
--- a/lib/bullet/ext/string.rb
+++ b/lib/bullet/ext/string.rb
@@ -4,13 +4,9 @@ module Bullet
   module Ext
     module String
       refine ::String do
-        attr_reader :bullet_class_name
-
         def bullet_class_name
-          @bullet_class_name ||= begin
-            last_colon = self.rindex(':')
-            last_colon ? self[0...last_colon] : self
-          end
+          last_colon = self.rindex(':')
+          last_colon ? self[0...last_colon].dup : self.dup
         end
       end
     end