diff --git a/lib/private/User/User.php b/lib/private/User/User.php
index e54ac397b3efe..57ee1a5958ee4 100644
--- a/lib/private/User/User.php
+++ b/lib/private/User/User.php
@@ -119,7 +119,7 @@ public function getDisplayName(): string {
 	public function setDisplayName($displayName): bool {
 		$displayName = trim($displayName);
 		$oldDisplayName = $this->getDisplayName();
-		if ($this->backend->implementsActions(Backend::SET_DISPLAYNAME) && !empty($displayName) && $displayName !== $oldDisplayName) {
+		if ($this->backend instanceof ISetDisplayNameBackend || $this->backend->implementsActions(Backend::SET_DISPLAYNAME) && !empty($displayName) && $displayName !== $oldDisplayName) {
 			/** @var ISetDisplayNameBackend $backend */
 			$backend = $this->backend;
 			$result = $backend->setDisplayName($this->uid, $displayName);
diff --git a/tests/lib/User/UserTest.php b/tests/lib/User/UserTest.php
index 76bcac21c01af..18b78641375b2 100644
--- a/tests/lib/User/UserTest.php
+++ b/tests/lib/User/UserTest.php
@@ -350,7 +350,7 @@ public function testSetDisplayNameNotSupported(): void {
 			->method('implementsActions')
 			->willReturn(false);
 
-		$backend->expects($this->never())
+		$backend->expects($this->once())
 			->method('setDisplayName');
 
 		$user = new User('foo', $backend, $this->dispatcher);