diff --git a/lib/private/NavigationManager.php b/lib/private/NavigationManager.php
index 468e2617d67f0..a20969c765a4b 100644
--- a/lib/private/NavigationManager.php
+++ b/lib/private/NavigationManager.php
@@ -312,7 +312,7 @@ public function setUnreadCounter(string $id, int $unreadCounter): void {
 	#[Override]
 	public function get(string $id): ?array {
 		$this->resolveAppNavigationEntries();
-		return $this->entries[$id];
+		return $this->entries[$id] ?? null;
 	}
 
 	#[Override]
diff --git a/tests/lib/NavigationManagerTest.php b/tests/lib/NavigationManagerTest.php
index 1b2805f9c0860..154456fe872c9 100644
--- a/tests/lib/NavigationManagerTest.php
+++ b/tests/lib/NavigationManagerTest.php
@@ -171,6 +171,13 @@ public function testAddClosure(array $entry, array $expectedEntry): void {
 		$this->assertEmpty($this->navigationManager->getAll('all'), 'Expected no navigation entry exists after clear()');
 	}
 
+	public function testGetUnknownEntryReturnsNull(): void {
+		// Requesting an entry no app has registered must return null without
+		// emitting an "Undefined array key" warning, e.g. when an app without
+		// a navigation entry renders a public page
+		$this->assertNull($this->navigationManager->get('unknown'));
+	}
+
 	public function testAddArrayClearGetAll(): void {
 		$entry = [
 			'id' => 'entry id',