diff --git a/phpseclib/Net/SFTP.php b/phpseclib/Net/SFTP.php
index fe937706..707808bb 100644
--- a/phpseclib/Net/SFTP.php
+++ b/phpseclib/Net/SFTP.php
@@ -1415,6 +1415,7 @@ class SFTP extends SSH2
             return true;
         }
 
+        $filename = $this->_realPath($filename);
         // rather than return what the permissions *should* be, we'll return what they actually are.  this will also
         // tell us if the file actually exists.
         // incidentally, SFTPv4+ adds an additional 32-bit integer field - flags - to the following:
diff --git a/tests/Functional/Net/SFTPUserStoryTest.php b/tests/Functional/Net/SFTPUserStoryTest.php
index fcc41eda..963ead41 100644
--- a/tests/Functional/Net/SFTPUserStoryTest.php
+++ b/tests/Functional/Net/SFTPUserStoryTest.php
@@ -240,6 +240,20 @@ class Functional_Net_SFTPUserStoryTest extends PhpseclibFunctionalTestCase
 
     /**
      * @depends testTruncate
+     * @group github850
+     */
+    public function testChModOnFile($sftp)
+    {
+        $this->assertNotFalse(
+            $sftp->chmod(0755, 'file1.txt'),
+            'Failed asserting that chmod() was successful.'
+        );
+
+        return $sftp;
+    }
+
+    /**
+     * @depends testChModOnFile
      */
     public function testChDirOnFile($sftp)
     {