diff --git a/core/modules/views/src/Plugin/views/filter/BooleanOperator.php b/core/modules/views/src/Plugin/views/filter/BooleanOperator.php
index 7078032..850f1c9 100644
--- a/core/modules/views/src/Plugin/views/filter/BooleanOperator.php
+++ b/core/modules/views/src/Plugin/views/filter/BooleanOperator.php
@@ -234,7 +234,7 @@ class BooleanOperator extends FilterPluginBase {
    *   (optional) Either static::EQUAL or static::NOT_EQUAL. Defaults to
    *   static::EQUAL.
    */
-  protected function queryOpBoolean($field, $query_operator = EQUAL) {
+  protected function queryOpBoolean($field, $query_operator = self::EQUAL) {
     if (empty($this->value)) {
       if ($this->accept_null) {
         if ($query_operator == static::EQUAL) {