diff --git a/test/test_downloader_fragment.py b/test/test_downloader_fragment.py
new file mode 100644
index 000000000..62a28ec92
--- /dev/null
+++ b/test/test_downloader_fragment.py
@@ -0,0 +1,102 @@
+#!/usr/bin/env python
+# coding: utf-8
+from __future__ import unicode_literals
+
+import json
+import os
+import shutil
+import sys
+import tempfile
+import threading
+import unittest
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from test.helper import FakeLogger, http_server_port
+from youtube_dl import YoutubeDL
+from youtube_dl.compat import compat_http_server
+from youtube_dl.downloader.dash import DashSegmentsFD
+
+
+FRAGMENTS = (b'first segment', b'second segment')
+
+
+class FragmentRequestHandler(compat_http_server.BaseHTTPRequestHandler):
+    def log_message(self, format, *args):
+        pass
+
+    def do_GET(self):
+        self.server.requests.append(self.path)
+        content = FRAGMENTS[int(self.path[1:])]
+        self.send_response(200)
+        self.send_header('Content-Length', str(len(content)))
+        self.end_headers()
+        self.wfile.write(content)
+
+
+class TestFragmentFD(unittest.TestCase):
+    def setUp(self):
+        self.directory = tempfile.mkdtemp()
+        self.filename = os.path.join(self.directory, 'video.mp4')
+        self.httpd = compat_http_server.HTTPServer(
+            ('127.0.0.1', 0), FragmentRequestHandler)
+        self.httpd.requests = []
+        self.server_thread = threading.Thread(target=self.httpd.serve_forever)
+        self.server_thread.daemon = True
+        self.server_thread.start()
+
+    def tearDown(self):
+        self.httpd.shutdown()
+        self.server_thread.join()
+        self.httpd.server_close()
+        shutil.rmtree(self.directory)
+
+    def prepare_partial(self, state):
+        with open(self.filename + '.part', 'wb') as stream:
+            stream.write(FRAGMENTS[0])
+        if state is not None:
+            with open(self.filename + '.ytdl', 'w') as stream:
+                stream.write(state)
+
+    def download(self, continuedl=True):
+        params = {'continuedl': continuedl, 'logger': FakeLogger()}
+        downloader = DashSegmentsFD(YoutubeDL(params), params)
+        self.assertTrue(downloader.real_download(self.filename, {
+            'fragments': [
+                {'url': 'http://127.0.0.1:%d/%d' % (
+                    http_server_port(self.httpd), index)}
+                for index in range(len(FRAGMENTS))],
+        }))
+        with open(self.filename, 'rb') as stream:
+            self.assertEqual(stream.read(), b''.join(FRAGMENTS))
+        self.assertFalse(os.path.exists(self.filename + '.part'))
+        self.assertFalse(os.path.exists(self.filename + '.ytdl'))
+
+    def test_fresh_download(self):
+        self.download()
+        self.assertEqual(self.httpd.requests, ['/0', '/1'])
+
+    def test_resume(self):
+        self.prepare_partial(json.dumps({
+            'downloader': {'current_fragment': {'index': 1}}}))
+        self.download()
+        self.assertEqual(self.httpd.requests, ['/1'])
+
+    def test_no_continue(self):
+        self.prepare_partial(json.dumps({
+            'downloader': {'current_fragment': {'index': 1}}}))
+        self.download(continuedl=False)
+        self.assertEqual(self.httpd.requests, ['/0', '/1'])
+
+    def test_no_continue_without_state(self):
+        self.prepare_partial(None)
+        self.download(continuedl=False)
+        self.assertEqual(self.httpd.requests, ['/0', '/1'])
+
+    def test_corrupt_state(self):
+        self.prepare_partial('{')
+        self.download()
+        self.assertEqual(self.httpd.requests, ['/0', '/1'])
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/youtube_dl/downloader/fragment.py b/youtube_dl/downloader/fragment.py
index 913e91b64..407089746 100644
--- a/youtube_dl/downloader/fragment.py
+++ b/youtube_dl/downloader/fragment.py
@@ -155,12 +155,9 @@ class FragmentFD(FileDownloader):
             }
         )
         tmpfilename = self.temp_name(ctx['filename'])
-        open_mode = 'wb'
 
         # Establish possible resume length
         resume_len = self.filesize_or_none(tmpfilename) or 0
-        if resume_len > 0:
-            open_mode = 'ab'
 
         # Should be initialized before ytdl file check
         ctx.update({
@@ -193,6 +190,7 @@ class FragmentFD(FileDownloader):
                 self._write_ytdl_file(ctx)
                 assert ctx['fragment_index'] == 0
 
+        open_mode = 'ab' if resume_len > 0 else 'wb'
         dest_stream, tmpfilename = sanitize_open(tmpfilename, open_mode)
 
         ctx.update({