diff --git a/ext/tag_list/main.php b/ext/tag_list/main.php
index 8788882f..6dd293ab 100644
--- a/ext/tag_list/main.php
+++ b/ext/tag_list/main.php
@@ -390,14 +390,15 @@ class TagList extends Extension {
 		}
 	}
 
-	private function add_refine_block(Page $page, /*string*/ $search) {
+	private function add_refine_block(Page $page, /*array(string)*/ $search) {
 		global $database;
 		global $config;
 
-		$related_tags = $database->cache->get("related_tags:$search");
+		$wild_tags = Tag::explode($search);
+		$str_search = Tag::implode($search);
+		$related_tags = $database->cache->get("related_tags:$str_search");
 
 		if(empty($related_tags)) {
-			$wild_tags = Tag::explode($search);
 			// $search_tags = array();
 
 			$tag_id_array = array();
@@ -434,7 +435,7 @@ class TagList extends Extension {
 				$args = array("limit"=>$config->get_int('tag_list_length'));
 
 				$related_tags = $database->get_all($query, $args);
-				$database->cache->set("related_tags:$search", $related_tags, 60*60);
+				$database->cache->set("related_tags:$str_search", $related_tags, 60*60);
 			}
 		}
 
diff --git a/ext/tag_list/theme.php b/ext/tag_list/theme.php
index 2ed81e74..0d175730 100644
--- a/ext/tag_list/theme.php
+++ b/ext/tag_list/theme.php
@@ -135,7 +135,9 @@ class TagListTheme extends Themelet {
 		$page->add_block(new Block("Refine Search", $html, "left", 60));
 	}
 
-	protected function ars($tag, $tags) {
+	protected function ars(/*string*/ $tag, /*array(string)*/ $tags) {
+		assert(is_array($tags));
+
 		// FIXME: a better fix would be to make sure the inputs are correct
 		$tag = strtolower($tag);
 		$tags = array_map("strtolower", $tags);