Index: wp-includes/link-template.php
===================================================================
--- wp-includes/link-template.php	(revision 22524)
+++ wp-includes/link-template.php	(working copy)
@@ -1246,8 +1246,8 @@
  * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
  */
 function adjacent_posts_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '') {
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', true);
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', false);
+	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories, true);
+	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories, false);
 }
 
 /**
@@ -1273,7 +1273,7 @@
  * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
  */
 function next_post_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '') {
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', false);
+	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories, false);
 }
 
 /**
@@ -1286,7 +1286,7 @@
  * @param array|string $excluded_categories Optional. Array or comma-separated list of excluded category IDs.
  */
 function prev_post_rel_link($title = '%title', $in_same_cat = false, $excluded_categories = '') {
-	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories = '', true);
+	echo get_adjacent_post_rel_link($title, $in_same_cat, $excluded_categories, true);
 }
 
 /**