diff --git a/lib/private/Files/Config/UserMountCache.php b/lib/private/Files/Config/UserMountCache.php
index e9e142d0d4..c9a701d24b 100644
--- a/lib/private/Files/Config/UserMountCache.php
+++ b/lib/private/Files/Config/UserMountCache.php
@@ -188,6 +188,9 @@ class UserMountCache implements IUserMountCache {
 
 	private function dbRowToMountInfo(array $row) {
 		$user = $this->userManager->get($row['user_id']);
+		if (is_null($user)) {
+			return null;
+		}
 		return new CachedMountInfo($user, (int)$row['storage_id'], (int)$row['root_id'], $row['mount_point'], $row['mount_id'], isset($row['path'])? $row['path']:'');
 	}
 
@@ -205,7 +208,7 @@ class UserMountCache implements IUserMountCache {
 
 			$rows = $query->execute()->fetchAll();
 
-			$this->mountsForUsers[$user->getUID()] = array_map([$this, 'dbRowToMountInfo'], $rows);
+			$this->mountsForUsers[$user->getUID()] = array_filter(array_map([$this, 'dbRowToMountInfo'], $rows));
 		}
 		return $this->mountsForUsers[$user->getUID()];
 	}
@@ -223,7 +226,7 @@ class UserMountCache implements IUserMountCache {
 
 		$rows = $query->execute()->fetchAll();
 
-		return array_map([$this, 'dbRowToMountInfo'], $rows);
+		return array_filter(array_map([$this, 'dbRowToMountInfo'], $rows));
 	}
 
 	/**
@@ -239,7 +242,7 @@ class UserMountCache implements IUserMountCache {
 
 		$rows = $query->execute()->fetchAll();
 
-		return array_map([$this, 'dbRowToMountInfo'], $rows);
+		return array_filter(array_map([$this, 'dbRowToMountInfo'], $rows));
 	}
 
 	/**