diff --git a/src/bundle/Controller/Content/ContentTreeController.php b/src/bundle/Controller/Content/ContentTreeController.php
index 29a10e06e6..372f914de5 100644
--- a/src/bundle/Controller/Content/ContentTreeController.php
+++ b/src/bundle/Controller/Content/ContentTreeController.php
@@ -23,6 +23,7 @@
 use Ibexa\Contracts\Core\Repository\Values\Content\Content;
 use Ibexa\Contracts\Core\Repository\Values\Content\Location;
 use Ibexa\Contracts\Core\Repository\Values\Content\Query;
+use Ibexa\Contracts\Core\Repository\Values\Content\Query\Criterion;
 use Ibexa\Contracts\Core\Repository\Values\User\Limitation;
 use Ibexa\Contracts\Core\SiteAccess\ConfigResolverInterface;
 use Ibexa\Rest\Message;
@@ -78,7 +79,7 @@ public function loadChildrenAction(
         int $parentLocationId,
         int $limit,
         int $offset,
-        Query\Criterion $filter
+        ?Criterion $filter
     ): Node {
         $location = $this->locationService->loadLocation($parentLocationId);
         $loadSubtreeRequestNode = new LoadSubtreeRequestNode($parentLocationId, $limit, $offset);
diff --git a/src/bundle/ControllerArgumentResolver/ContentTreeChildrenQueryArgumentResolver.php b/src/bundle/ControllerArgumentResolver/ContentTreeChildrenQueryArgumentResolver.php
index 2f42f3e7d9..653bfd48ed 100644
--- a/src/bundle/ControllerArgumentResolver/ContentTreeChildrenQueryArgumentResolver.php
+++ b/src/bundle/ControllerArgumentResolver/ContentTreeChildrenQueryArgumentResolver.php
@@ -40,13 +40,20 @@ public function supports(Request $request, ArgumentMetadata $argument): bool
     }
 
     /**
-     * @return iterable<\Ibexa\Contracts\Core\Repository\Values\Content\Query\Criterion>
+     * @return iterable<\Ibexa\Contracts\Core\Repository\Values\Content\Query\Criterion|null>
      *
      * @throws \Ibexa\Contracts\Core\Repository\Exceptions\InvalidArgumentException
      */
     public function resolve(Request $request, ArgumentMetadata $argument): iterable
     {
-        yield new LogicalAnd($this->processFilterQueryCriteria($request));
+        $criteria = $this->processFilterQueryCriteria($request);
+        if ($argument->isNullable() && empty($criteria)) {
+            yield null;
+
+            return;
+        }
+
+        yield new LogicalAnd($criteria);
     }
 
     /**