diff --git a/apps/dav/lib/SystemTag/SystemTagMappingNode.php b/apps/dav/lib/SystemTag/SystemTagMappingNode.php
index ba6f9d23ad4..96180d0e0d6 100644
--- a/apps/dav/lib/SystemTag/SystemTagMappingNode.php
+++ b/apps/dav/lib/SystemTag/SystemTagMappingNode.php
@@ -114,7 +114,8 @@ class SystemTagMappingNode implements \Sabre\DAV\INode {
 			if (!$this->tagManager->canUserAssignTag($this->tag, $this->user)) {
 				throw new Forbidden('No permission to unassign tag ' . $this->tag->getId());
 			}
-			if (!($this->childWriteAccessFunction)($this->objectId)) {
+			$writeAccessFunction = $this->childWriteAccessFunction;
+			if (!$writeAccessFunction($this->objectId)) {
 				throw new Forbidden('No permission to unassign tag to ' . $this->objectId);
 			}
 			$this->tagMapper->unassignTags($this->objectId, $this->objectType, $this->tag->getId());
diff --git a/apps/dav/lib/SystemTag/SystemTagsObjectMappingCollection.php b/apps/dav/lib/SystemTag/SystemTagsObjectMappingCollection.php
index 4f46c580c51..38b2c3b2f82 100644
--- a/apps/dav/lib/SystemTag/SystemTagsObjectMappingCollection.php
+++ b/apps/dav/lib/SystemTag/SystemTagsObjectMappingCollection.php
@@ -61,7 +61,8 @@ class SystemTagsObjectMappingCollection implements ICollection {
 			if (!$this->tagManager->canUserAssignTag($tag, $this->user)) {
 				throw new Forbidden('No permission to assign tag ' . $tagId);
 			}
-			if (!($this->childWriteAccessFunction)($this->objectId)) {
+			$writeAccessFunction = $this->childWriteAccessFunction;
+			if (!$writeAccessFunction($this->objectId)) {
 				throw new Forbidden('No permission to assign tag to ' . $this->objectId);
 			}
 			$this->tagMapper->assignTags($this->objectId, $this->objectType, $tagId);