diff --git a/lib/private/Federation/CloudIdManager.php b/lib/private/Federation/CloudIdManager.php
index fa8ac0fa0c2b8..a7d36eda4a031 100644
--- a/lib/private/Federation/CloudIdManager.php
+++ b/lib/private/Federation/CloudIdManager.php
@@ -119,6 +119,9 @@ public function resolveCloudId(string $cloudId): ICloudId {
 	public function getDisplayNameFromContact(string $cloudId): ?string {
 		$cachedName = $this->displayNameCache->get($cloudId);
 		if ($cachedName !== null) {
+			if ($cachedName === $cloudId) {
+				return null;
+			}
 			return $cachedName;
 		}
 
@@ -138,8 +141,8 @@ public function getDisplayNameFromContact(string $cloudId): ?string {
 							$this->displayNameCache->set($cloudId, $entry['FN'], 15 * 60);
 							return $entry['FN'];
 						} else {
-							$this->displayNameCache->set($cloudId, $cloudID, 15 * 60);
-							return $cloudID;
+							$this->displayNameCache->set($cloudId, $cloudId, 15 * 60);
+							return null;
 						}
 					}
 				}
diff --git a/tests/lib/Federation/CloudIdManagerTest.php b/tests/lib/Federation/CloudIdManagerTest.php
index 14daef2714227..1775c18a5e912 100644
--- a/tests/lib/Federation/CloudIdManagerTest.php
+++ b/tests/lib/Federation/CloudIdManagerTest.php
@@ -56,6 +56,34 @@ protected function setUp(): void {
 		$this->overwriteService(ICloudIdManager::class, $this->cloudIdManager);
 	}
 
+	public function dataGetDisplayNameFromContact(): array {
+		return [
+			['test1@example.tld', 'test', 'test'],
+			['test2@example.tld', null, null],
+			['test3@example.tld', 'test3@example', 'test3@example'],
+			['test4@example.tld', 'test4@example.tld', null],
+		];
+	}
+
+	/**
+	 * @dataProvider dataGetDisplayNameFromContact
+	 */
+	public function testGetDisplayNameFromContact(string $cloudId, ?string $displayName, ?string $expected): void {
+		$returnedContact = [
+			'CLOUD' => [$cloudId],
+			'FN' => $expected,
+		];
+		if ($displayName === null) {
+			unset($returnedContact['FN']);
+		}
+		$this->contactsManager->method('search')
+			->with($cloudId, ['CLOUD'])
+			->willReturn([$returnedContact]);
+
+		$this->assertEquals($expected, $this->cloudIdManager->getDisplayNameFromContact($cloudId));
+		$this->assertEquals($expected, $this->cloudIdManager->getDisplayNameFromContact($cloudId));
+	}
+
 	public function cloudIdProvider(): array {
 		return [
 			['test@example.com', 'test', 'example.com', 'test@example.com'],