Index: _test_real_ftp.py
===================================================================
--- _test_real_ftp.py (revision 869:808476873684)
+++ _test_real_ftp.py (revision 873:4f4a4541b97a)
@@ -570,5 +570,16 @@
     #
     def test_open_for_reading(self):
-        # test for issue #17, http://ftputil.sschwarzer.net/trac/ticket/17
+        # test for issues #17 and #51,
+        #  http://ftputil.sschwarzer.net/trac/ticket/17 and
+        #  http://ftputil.sschwarzer.net/trac/ticket/51
+        file1 = self.host.file("debian-keyring.tar.gz", 'rb')
+        time.sleep(1)
+        # depending on the FTP server, this might return a status code
+        #  unexpected by `ftplib`, or block the socket connection until
+        #  a server-side timeout
+        file1.close()
+
+    def test_subsequent_reading(self):
+        # opening a file for reading
         file1 = self.host.file("debian-keyring.tar.gz", 'rb')
         file1.close()
@@ -615,3 +626,5 @@
     server, user, password = get_login_data()
     unittest.main()
-
+    import __main__
+    #unittest.main(__main__, "RealFTPTest.test_open_for_reading")
+
Index: ftp_file.py
===================================================================
--- ftp_file.py (revision 869:808476873684)
+++ ftp_file.py (revision 873:4f4a4541b97a)
@@ -216,8 +216,10 @@
                 ftp_error._try_with_ioerror(self._session.voidresp)
             except ftp_error.FTPIOError, exception:
-                # ignore some errors, see ticket #17 at
-                #  http://ftputil.sschwarzer.net/trac/ticket/17
+                # ignore some errors, see tickets #51 and #17 at
+                #  http://ftputil.sschwarzer.net/trac/ticket/51 and
+                #  http://ftputil.sschwarzer.net/trac/ticket/17,
+                #  respectively
                 error_code = str(exception).split()[0]
-                if error_code not in ("426", "450", "451"):
+                if error_code not in ("150", "426", "450", "451"):
                     raise
         finally: