diff --git a/core/modules/views/src/Plugin/views/filter/InOperator.php b/core/modules/views/src/Plugin/views/filter/InOperator.php
index 36089e05aec..cee717c0f8d 100644
--- a/core/modules/views/src/Plugin/views/filter/InOperator.php
+++ b/core/modules/views/src/Plugin/views/filter/InOperator.php
@@ -331,7 +331,7 @@ public function adminSummary() {
 
     $this->getValueOptions();
     // Some filter_in_operator usage uses optgroups forms, so flatten it.
-    $flat_options = OptGroup::flattenOptions($this->valueOptions);
+    $flat_options = isset($this->valueOptions) ? OptGroup::flattenOptions($this->valueOptions) : [];
 
     if (!is_array($this->value)) {
       return;