diff --git a/lib/private/session/internal.php b/lib/private/session/internal.php
index 49b52b5c79..a7c9e2fdef 100644
--- a/lib/private/session/internal.php
+++ b/lib/private/session/internal.php
@@ -35,7 +35,9 @@ class Internal extends Memory {
 	 */
 	public function remove($key) {
 		// also remove it from $_SESSION to prevent re-setting the old value during the merge
-		unset($_SESSION[$key]);
+		if (isset($_SESSION[$key])) {
+			unset($_SESSION[$key]);
+		}
 		parent::remove($key);
 	}