diff -u b/core/modules/node/node.api.php b/core/modules/node/node.api.php
--- b/core/modules/node/node.api.php
+++ b/core/modules/node/node.api.php
@@ -27,7 +27,8 @@
  * module; it is common to use role IDs as grant IDs, but that is not required.
  * Your module could instead maintain its own list of users, where each list has
  * an ID. In that case, the return value of this hook would be an array of the
- * list IDs that this user is a member of. Do not use 'all' as a realm.
+ * list IDs that this user is a member of. 'all' is a reserved realm and can't
+ * be used.
  *
  * A node access module may implement as many realms as necessary to properly
  * define the access privileges for the nodes. Note that the system makes no
diff -u b/core/modules/node/src/NodeGrantDatabaseStorage.php b/core/modules/node/src/NodeGrantDatabaseStorage.php
--- b/core/modules/node/src/NodeGrantDatabaseStorage.php
+++ b/core/modules/node/src/NodeGrantDatabaseStorage.php
@@ -108,6 +108,7 @@
    */
   public function checkAll(AccountInterface $account) {
     $query = $this->database->select('node_access');
+    // The method should return 0 or 1 so start with SELECT 1.
     $query->addExpression('1');
     $query
       ->condition('nid', 0)
@@ -118,7 +119,9 @@
     if (count($grants) > 0 ) {
       $query->condition($grants);
     }
-    return (int) $query->execute()->fetchField();
+    // The query either returns 1 from SELECT 1 or FALSE, cast to int to make
+    // sure the return value is 0 or 1 as prescribed on the interface.
+    return (int) $query->range(0, 1)->execute()->fetchField();
   }
 
   /**