Index: wp-content/themes/twentyeleven/editor-blocks.css
===================================================================
--- wp-content/themes/twentyeleven/editor-blocks.css	(revision 53622)
+++ wp-content/themes/twentyeleven/editor-blocks.css	(working copy)
@@ -433,6 +433,10 @@
 	text-align: center;
 }
 
+[data-align="center"] .wp-block-categories{
+    text-align: center;
+}
+
 /* Latest Comments */
 
 .wp-block-latest-comments {