diff --git a/module/VuFind/src/VuFind/Related/Similar.php b/module/VuFind/src/VuFind/Related/Similar.php
index 2478352dcc860347df48e6536379b1d08a758364..4401fad8438068760836cdc8df9b433f2bf2e99a 100644
--- a/module/VuFind/src/VuFind/Related/Similar.php
+++ b/module/VuFind/src/VuFind/Related/Similar.php
@@ -72,8 +72,9 @@ class Similar implements RelatedInterface
      */
     public function init($settings, $driver)
     {
-        $this->results
-            = $this->searchService->similar('Solr', $driver->getUniqueId());
+        $this->results = $this->searchService->similar(
+            $driver->getSourceIdentifier(), $driver->getUniqueId()
+        );
     }
 
     /**