diff --git a/wp-includes/post-template.php b/wp-includes/post-template.php
index 034248c6f6..7eb7a2fe2e 100644
--- a/wp-includes/post-template.php
+++ b/wp-includes/post-template.php
@@ -616,18 +616,27 @@ function wp_link_pages($args = '') {
 	return $output;
 }
 
+/**
+ * Helper function for wp_link_pages().
+ *
+ * @since 3.1.0
+ * @access private
+ *
+ * @param $i Page number.
+ * @return string Link.
+ */
 function _wp_link_page( $i ) {
 	global $post, $wp_rewrite;
 
 	if ( 1 == $i ) {
-		$url .= get_permalink();
+		$url = get_permalink();
 	} else {
 		if ( '' == get_option('permalink_structure') || in_array($post->post_status, array('draft', 'pending')) )
 			$url = add_query_arg( 'page', $i, get_permalink() );
 		elseif ( 'page' == get_option('show_on_front') && get_option('page_on_front') == $post->ID )
 			$url = trailingslashit(get_permalink()) . user_trailingslashit("$wp_rewrite->pagination_base/" . $i, 'single_paged');
 		else
-			$url .= trailingslashit(get_permalink()) . user_trailingslashit($i, 'single_paged');
+			$url = trailingslashit(get_permalink()) . user_trailingslashit($i, 'single_paged');
 	}
 
 	return '<a href="' . $url  . '">';