diff --git a/src/Controller/RelatedRorController.php b/src/Controller/RelatedRorController.php
index 27e4076..534d522 100644
--- a/src/Controller/RelatedRorController.php
+++ b/src/Controller/RelatedRorController.php
@@ -125,8 +125,8 @@ class RelatedRorController extends ControllerBase {
     }
 
     private function getSimilarity(array $orig, array $other): int {
-        if(!in_array('field_tags', $orig) || count($orig['field_tags']) == 0 || 
-            !in_array('field_tags', $other) || count($other['field_tags']) == 0) {
+        if(!array_key_exists('field_tags', $orig) || count($orig['field_tags']) == 0 || 
+            !array_key_exists('field_tags', $other) || count($other['field_tags']) == 0) {
             return 0;
         }
         $orig_tags = array_map(function($t) { return $t['target_id']; }, $orig['field_tags']);