diff --git a/apps/user_ldap/lib/Group_LDAP.php b/apps/user_ldap/lib/Group_LDAP.php
index d5a1cab30fe..723b3d856ad 100644
--- a/apps/user_ldap/lib/Group_LDAP.php
+++ b/apps/user_ldap/lib/Group_LDAP.php
@@ -797,7 +797,7 @@ class Group_LDAP extends BackendUtility implements GroupInterface, IGroupLDAP, I
 		}
 		$seen[$dn] = true;
 
-		if ($this->cachedGroupsByMember[$dn]) {
+		if (isset($this->cachedGroupsByMember[$dn])) {
 			return $this->cachedGroupsByMember[$dn];
 		}