Index: wp-includes/taxonomy.php
===================================================================
--- wp-includes/taxonomy.php	(revision 21842)
+++ wp-includes/taxonomy.php	(working copy)
@@ -1681,7 +1681,7 @@
  *
  * @param string $taxonomy Taxonomy name
  * @param array|string $args Overwrite defaults. See get_terms()
- * @return int How many terms are in $taxonomy
+ * @return int|WP_Error How many terms are in $taxonomy. WP_Error if $taxonomy does not exist.
  */
 function wp_count_terms( $taxonomy, $args = array() ) {
 	$defaults = array('hide_empty' => false);