diff --git a/apps/files_external/ajax/addRootCertificate.php b/apps/files_external/ajax/addRootCertificate.php
index c192855629209e5b45491ca9f5339f30a5f43fe2..c5f49a82d365c8994a7754899b4938744707aa9f 100644
--- a/apps/files_external/ajax/addRootCertificate.php
+++ b/apps/files_external/ajax/addRootCertificate.php
@@ -17,6 +17,7 @@ if (!strpos($data, 'BEGIN CERTIFICATE')) {
 	$pem = "-----BEGIN CERTIFICATE-----\n".$pem."-----END CERTIFICATE-----\n";
 	$fh = fopen($to, 'w');
 	fwrite($fh, $pem);
+	fclose($fh);
 }
 
 OC_Mount_Config::createCertificateBundle();