diff --git a/apps/files_external/lib/Lib/Storage/SFTP.php b/apps/files_external/lib/Lib/Storage/SFTP.php
index 532c50808db23..664e063b586cb 100644
--- a/apps/files_external/lib/Lib/Storage/SFTP.php
+++ b/apps/files_external/lib/Lib/Storage/SFTP.php
@@ -36,15 +36,19 @@
  */
 namespace OCA\Files_External\Lib\Storage;
 
+use Icewind\Streams\CallbackWrapper;
 use Icewind\Streams\IteratorDirectory;
 use Icewind\Streams\RetryWrapper;
+use OC\Files\Storage\Common;
+use OCP\Cache\CappedMemoryCache;
+use OCP\Files\Storage\IWriteStreamStorage;
 use phpseclib\Net\SFTP\Stream;
 
 /**
  * Uses phpseclib's Net\SFTP class and the Net\SFTP\Stream stream wrapper to
  * provide access to SFTP servers.
  */
-class SFTP extends \OC\Files\Storage\Common {
+class SFTP extends Common implements IWriteStreamStorage {
 	private $host;
 	private $user;
 	private $root;
@@ -56,6 +60,7 @@ class SFTP extends \OC\Files\Storage\Common {
 	 * @var \phpseclib\Net\SFTP
 	 */
 	protected $client;
+	private CappedMemoryCache $knownMTimes;
 
 	/**
 	 * @param string $host protocol://server:port
@@ -111,6 +116,8 @@ public function __construct($params) {
 
 		$this->root = '/' . ltrim($this->root, '/');
 		$this->root = rtrim($this->root, '/') . '/';
+
+		$this->knownMTimes = new CappedMemoryCache();
 	}
 
 	/**
@@ -368,6 +375,7 @@ public function unlink($path) {
 	 * {@inheritdoc}
 	 */
 	public function fopen($path, $mode) {
+		$path = $this->cleanPath($path);
 		try {
 			$absPath = $this->absPath($path);
 			switch ($mode) {
@@ -384,7 +392,13 @@ public function fopen($path, $mode) {
 				case 'wb':
 					SFTPWriteStream::register();
 					$context = stream_context_create(['sftp' => ['session' => $this->getConnection()]]);
-					return fopen('sftpwrite://' . trim($absPath, '/'), 'w', false, $context);
+					$fh = fopen('sftpwrite://' . trim($absPath, '/'), 'w', false, $context);
+					if ($fh) {
+						$fh = CallbackWrapper::wrap($fh, null, null, function() use ($path) {
+							$this->knownMTimes->set($path, time());
+						});
+					}
+					return $fh;
 				case 'a':
 				case 'ab':
 				case 'r+':
@@ -413,14 +427,13 @@ public function touch($path, $mtime = null) {
 				return false;
 			}
 			if (!$this->file_exists($path)) {
-				$this->getConnection()->put($this->absPath($path), '');
+				return $this->getConnection()->put($this->absPath($path), '');
 			} else {
 				return false;
 			}
 		} catch (\Exception $e) {
 			return false;
 		}
-		return true;
 	}
 
 	/**
@@ -454,11 +467,17 @@ public function rename($source, $target) {
 	 */
 	public function stat($path) {
 		try {
+			$this->cleanPath($path);
 			$stat = $this->getConnection()->stat($this->absPath($path));
 
 			$mtime = $stat ? $stat['mtime'] : -1;
 			$size = $stat ? $stat['size'] : 0;
 
+			// the mtime can't be less than when we last touched it
+			if ($knownMTime = $this->knownMTimes->get($path)) {
+				$mtime = max($mtime, $knownMTime);
+			}
+
 			return ['mtime' => $mtime, 'size' => $size, 'ctime' => -1];
 		} catch (\Exception $e) {
 			return false;