diff -r 29ea3827cfaa Lib/ftplib.py
--- a/Lib/ftplib.py	Mon Dec 21 14:17:12 2015 -0600
+++ b/Lib/ftplib.py	Thu Dec 24 11:41:07 2015 +0100
@@ -444,7 +444,12 @@
                 data = conn.recv(blocksize)
                 if not data:
                     break
-                callback(data)
+                try:
+                    callback(data)
+                except Exception:
+                    self.voidresp()
+                    raise
+
             # shutdown ssl layer
             if _SSLSocket is not None and isinstance(conn, _SSLSocket):
                 conn.unwrap()
@@ -479,7 +484,11 @@
                     line = line[:-2]
                 elif line[-1:] == '\n':
                     line = line[:-1]
-                callback(line)
+                try:
+                    callback(line)
+                except Exception:
+                    self.voidresp()
+                    raise
             # shutdown ssl layer
             if _SSLSocket is not None and isinstance(conn, _SSLSocket):
                 conn.unwrap()
diff -r 29ea3827cfaa Lib/test/test_ftplib.py
--- a/Lib/test/test_ftplib.py	Mon Dec 21 14:17:12 2015 -0600
+++ b/Lib/test/test_ftplib.py	Thu Dec 24 11:41:07 2015 +0100
@@ -573,6 +573,14 @@
         self.client.retrlines('retr', received.append)
         self.check_data(''.join(received), RETR_DATA.replace('\r\n', ''))
 
+    def test_faulty_callback(self):
+        def callback():
+            pass
+        self.assertRaises(Exception, self.client.retrbinary, 'retr', callback)
+        self.assertEqual(self.client.sendcmd('noop'), '200 noop ok')
+        self.assertRaises(Exception, self.client.retrlines, 'retr', callback)
+        self.assertEqual(self.client.sendcmd('noop'), '200 noop ok')
+
     def test_storbinary(self):
         f = io.BytesIO(RETR_DATA.encode('ascii'))
         self.client.storbinary('stor', f)