diff --git a/lib/compass/sprite_importer.rb b/lib/compass/sprite_importer.rb
index 0d92fda9..e2948271 100644
--- a/lib/compass/sprite_importer.rb
+++ b/lib/compass/sprite_importer.rb
@@ -81,7 +81,7 @@ module Compass
 
     # Returns an Array of image names without the file extension
     def sprite_names
-      @sprite_names ||= files.collect do |file|
+      files.collect do |file|
         filename = File.basename(file, '.png')
         unless VAILD_FILE_NAME =~ filename
           raise Compass::Error, "Sprite file names must be legal css identifiers. Please rename #{File.basename(file)}"