Index: README.txt
===================================================================
--- README.txt	(revision 33)
+++ README.txt	(working copy)
@@ -73,9 +73,9 @@
  */
 function YOURTHEME_preprocess_block(&$variables) {
   if (isset($variables['block_class'])) {
-    $variables['block_classes'] .= ' '. block_class($block);
+    $variables['block_classes'] .= ' '. block_class($variables['block']);
   }
   else {
-    $variables['block_classes'] = block_class($block);
+    $variables['block_classes'] = block_class($variables['block']);
   }
 }