diff --git a/lib/public/IUser.php b/lib/public/IUser.php
index ce9cf0096ec..daf993df6cd 100644
--- a/lib/public/IUser.php
+++ b/lib/public/IUser.php
@@ -112,10 +112,10 @@ interface IUser {
 
 	/**
 	 * Get the backend for the current user object
-	 *
+	 * @return ?UserInterface
 	 * @since 15.0.0
 	 */
-	public function getBackend(): ?UserInterface;
+	public function getBackend();
 
 	/**
 	 * check if the backend allows the user to change his avatar on Personal page