Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 17468)
+++ wp-includes/taxonomy.php	(working copy)
@@ -353,6 +353,7 @@
 
 	$args['name'] = $taxonomy;
 	$args['object_type'] = (array) $object_type;
+	$args['object_type'] = array_map( 'sanitize_key', $args['object_type'] );
 
 	$args['labels'] = get_taxonomy_labels( (object) $args );
 	$args['label'] = $args['labels']->name;