diff --git a/apps/files/lib/helper.php b/apps/files/lib/helper.php
index aa5a2f8c68a..97b9d8e7044 100644
--- a/apps/files/lib/helper.php
+++ b/apps/files/lib/helper.php
@@ -82,7 +82,7 @@ class Helper
 	public static function compareTimestamp(FileInfo $a, FileInfo $b) {
 		$aTime = $a->getMTime();
 		$bTime = $b->getMTime();
-		return $aTime - $bTime;
+		return ($aTime < $bTime) ? -1 : 1;
 	}
 
 	/**
diff --git a/apps/files/tests/helper.php b/apps/files/tests/helper.php
index da902f4f78a..1b7c8eef43a 100644
--- a/apps/files/tests/helper.php
+++ b/apps/files/tests/helper.php
@@ -33,10 +33,10 @@ class Test_Files_Helper extends \Test\TestCase {
 	 */
 	private function getTestFileList() {
 		return array(
-			self::makeFileInfo('a.txt', 4, 1000),
+			self::makeFileInfo('a.txt', 4, 2.3 * pow(10, 9)),
 			self::makeFileInfo('q.txt', 5, 150),
 			self::makeFileInfo('subdir2', 87, 128, true),
-			self::makeFileInfo('b.txt', 166, 800),
+			self::makeFileInfo('b.txt', 2.2 * pow(10, 9), 800),
 			self::makeFileInfo('o.txt', 12, 100),
 			self::makeFileInfo('subdir', 88, 125, true),
 		);