diff --git a/lib/bullet/detector/n_plus_one_query.rb b/lib/bullet/detector/n_plus_one_query.rb
index 7a6600e1..650ea3c9 100644
--- a/lib/bullet/detector/n_plus_one_query.rb
+++ b/lib/bullet/detector/n_plus_one_query.rb
@@ -27,7 +27,7 @@ def call_association(object, associations)
           )
           if !excluded_stacktrace_path? && conditions_met?(object, associations)
             Bullet.debug('detect n + 1 query', "object: #{object.bullet_key}, associations: #{associations}")
-            create_notification caller_in_project(object.bullet_key), object.class.to_s, associations
+            create_notification(caller_in_project(object.bullet_key), object.class.to_s, associations)
           end
         end
 
@@ -38,16 +38,16 @@ def add_possible_objects(object_or_objects)
           objects = Array.wrap(object_or_objects)
           class_names_match_regex = true
           primary_key_values_are_empty = true
-          keys_joined = ""
-          objects.each do |obj|
+
+          keys_joined = objects.map do |obj|
             unless obj.class.name =~ /^HABTM_/
               class_names_match_regex = false
             end
             unless obj.bullet_primary_key_value.nil?
               primary_key_values_are_empty = false
             end
-            keys_joined += "#{(keys_joined.empty? ? '' : ', ')}#{obj.bullet_key}"
-          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/object.rb b/lib/bullet/ext/object.rb
index 68dfbc87..f8e60cbb 100644
--- a/lib/bullet/ext/object.rb
+++ b/lib/bullet/ext/object.rb
@@ -4,22 +4,20 @@ module Bullet
   module Ext
     module Object
       refine ::Object do
+        attr_writer :bullet_key, :bullet_primary_key_value
+
         def bullet_key
-          "#{self.class}:#{bullet_primary_key_value}"
+          @bullet_key ||= "#{self.class}:#{bullet_primary_key_value}"
         end
 
         def bullet_primary_key_value
-          return if respond_to?(:persisted?) && !persisted?
-
-          if self.class.respond_to?(:primary_keys) && self.class.primary_keys
-            primary_key = self.class.primary_keys
-          elsif self.class.respond_to?(:primary_key) && self.class.primary_key
-            primary_key = self.class.primary_key
-          else
-            primary_key = :id
-          end
+          @bullet_primary_key_value ||= begin
+            return if respond_to?(:persisted?) && !persisted?
 
-          bullet_join_potential_composite_primary_key(primary_key)
+            primary_key = self.class.try(:primary_keys) || self.class.try(:primary_key) || :id
+
+            bullet_join_potential_composite_primary_key(primary_key)
+          end
         end
 
         private
diff --git a/lib/bullet/ext/string.rb b/lib/bullet/ext/string.rb
index 1b9e9413..ed4ee285 100644
--- a/lib/bullet/ext/string.rb
+++ b/lib/bullet/ext/string.rb
@@ -4,8 +4,13 @@ module Bullet
   module Ext
     module String
       refine ::String do
+        attr_reader :bullet_class_name
+
         def bullet_class_name
-          sub(/:[^:]*?$/, '')
+          @bullet_class_name ||= begin
+            last_colon = self.rindex(':')
+            last_colon ? self[0...last_colon] : self
+          end
         end
       end
     end