diff --git a/plugins/cache/content.inc b/plugins/cache/content.inc
index 25b804c..02eb661 100644
--- a/plugins/cache/content.inc
+++ b/plugins/cache/content.inc
@@ -279,7 +279,9 @@ function panels_content_cache_get_base_cid($display) {
     $cid[] = 'owner_' . $display->owner->id;
   }
 
-  $cid[] = 'did_' . $display->did;
+  if (isset($display->did)) {
+    $cid[] = 'did_' . $display->did;
+  }
 
   return $cid;
 }