diff --git a/lib/stringex/acts_as_url/adapter/base.rb b/lib/stringex/acts_as_url/adapter/base.rb
index b8ed8b19..9bf0fe37 100644
--- a/lib/stringex/acts_as_url/adapter/base.rb
+++ b/lib/stringex/acts_as_url/adapter/base.rb
@@ -18,7 +18,7 @@ def create_callbacks!(klass)
         end
 
         def ensure_unique_url!(instance)
-          @url_owners = nil
+          @taken_urls = nil
           self.instance = instance
 
           handle_url!
@@ -131,7 +131,7 @@ def url_taken?(url)
           if settings.url_taken_method
             instance.send(settings.url_taken_method, url)
           else
-            url_owners.any?{|owner| url_attribute_for(owner) == url}
+            taken_urls.include?(url)
           end
         end
 
@@ -196,8 +196,9 @@ def url_owner_conditions
           @url_owner_conditions
         end
 
-        def url_owners
-          @url_owners ||= url_owners_class.unscoped.where(url_owner_conditions).to_a
+        def taken_urls
+          @taken_urls ||= url_owners_class.unscoped.where(url_owner_conditions).
+                          pluck(settings.url_attribute)
         end
 
         def url_owners_class
diff --git a/lib/stringex/acts_as_url/adapter/data_mapper.rb b/lib/stringex/acts_as_url/adapter/data_mapper.rb
index 67fdbf63..d77042ea 100644
--- a/lib/stringex/acts_as_url/adapter/data_mapper.rb
+++ b/lib/stringex/acts_as_url/adapter/data_mapper.rb
@@ -44,8 +44,10 @@ def read_attribute(instance, attribute)
           instance.attributes[attribute]
         end
 
-        def url_owners
-          @url_owners ||= url_owners_class.all(:conditions => url_owner_conditions)
+        def taken_urls
+          @taken_urls ||= url_owners_class.
+                          all(conditions: url_owner_conditions).
+                          pluck(settings.url_attribute)
         end
 
         def read_attribute(instance, name)
@@ -62,4 +64,4 @@ def self.orm_class
       end
     end
   end
-end
\ No newline at end of file
+end