diff --git a/youtube_dl/downloader/dash.py b/youtube_dl/downloader/dash.py
index 94a13a5433..7491fdad85 100644
--- a/youtube_dl/downloader/dash.py
+++ b/youtube_dl/downloader/dash.py
@@ -28,7 +28,7 @@ def real_download(self, filename, info_dict):
         frag_index = 0
         for i, segment in enumerate(segments):
             frag_index += 1
-            if frag_index <= ctx['frag_index']:
+            if frag_index <= ctx['fragment_index']:
                 continue
             # In DASH, the first segment contains necessary headers to
             # generate a valid MP4 file, so always abort for the first segment
diff --git a/youtube_dl/downloader/f4m.py b/youtube_dl/downloader/f4m.py
index e456ed58f6..c8fde9a890 100644
--- a/youtube_dl/downloader/f4m.py
+++ b/youtube_dl/downloader/f4m.py
@@ -376,7 +376,7 @@ def real_download(self, filename, info_dict):
         while fragments_list:
             seg_i, frag_i = fragments_list.pop(0)
             frag_index += 1
-            if frag_index <= ctx['frag_index']:
+            if frag_index <= ctx['fragment_index']:
                 continue
             name = 'Seg%d-Frag%d' % (seg_i, frag_i)
             query = []
diff --git a/youtube_dl/downloader/fragment.py b/youtube_dl/downloader/fragment.py
index 80bb14d61b..6c02cfc982 100644
--- a/youtube_dl/downloader/fragment.py
+++ b/youtube_dl/downloader/fragment.py
@@ -66,7 +66,9 @@ def _append_fragment(self, ctx, frag_content):
         if not (ctx.get('live') or ctx['tmpfilename'] == '-'):
             frag_index_stream, _ = sanitize_open(self.ytdl_filename(ctx['filename']), 'w')
             frag_index_stream.write(json.dumps({
-                'frag_index': ctx['frag_index']
+                'download': {
+                    'last_fragment_index': ctx['fragment_index']
+                },
             }))
             frag_index_stream.close()
 
@@ -100,7 +102,7 @@ def _prepare_frag_download(self, ctx):
             ytdl_filename = encodeFilename(self.ytdl_filename(ctx['filename']))
             if os.path.isfile(ytdl_filename):
                 frag_index_stream, _ = sanitize_open(ytdl_filename, 'r')
-                frag_index = json.loads(frag_index_stream.read())['frag_index']
+                frag_index = json.loads(frag_index_stream.read())['download']['last_fragment_index']
                 frag_index_stream.close()
         dest_stream, tmpfilename = sanitize_open(tmpfilename, open_mode)
 
@@ -108,7 +110,7 @@ def _prepare_frag_download(self, ctx):
             'dl': dl,
             'dest_stream': dest_stream,
             'tmpfilename': tmpfilename,
-            'frag_index': frag_index,
+            'fragment_index': frag_index,
             # Total complete fragments downloaded so far in bytes
             'complete_frags_downloaded_bytes': resume_len,
         })
@@ -120,8 +122,8 @@ def _start_frag_download(self, ctx):
         state = {
             'status': 'downloading',
             'downloaded_bytes': ctx['complete_frags_downloaded_bytes'],
-            'frag_index': ctx['frag_index'],
-            'frag_count': total_frags,
+            'fragment_index': ctx['fragment_index'],
+            'fragment_count': total_frags,
             'filename': ctx['filename'],
             'tmpfilename': ctx['tmpfilename'],
         }
@@ -144,12 +146,12 @@ def frag_progress_hook(s):
             if not ctx['live']:
                 estimated_size = (
                     (ctx['complete_frags_downloaded_bytes'] + frag_total_bytes) /
-                    (state['frag_index'] + 1) * total_frags)
+                    (state['fragment_index'] + 1) * total_frags)
                 state['total_bytes_estimate'] = estimated_size
 
             if s['status'] == 'finished':
-                state['frag_index'] += 1
-                ctx['frag_index'] = state['frag_index']
+                state['fragment_index'] += 1
+                ctx['fragment_index'] = state['fragment_index']
                 state['downloaded_bytes'] += frag_total_bytes - ctx['prev_frag_downloaded_bytes']
                 ctx['complete_frags_downloaded_bytes'] = state['downloaded_bytes']
                 ctx['prev_frag_downloaded_bytes'] = 0
diff --git a/youtube_dl/downloader/hls.py b/youtube_dl/downloader/hls.py
index 9a87d7ca89..0e29c8a2ad 100644
--- a/youtube_dl/downloader/hls.py
+++ b/youtube_dl/downloader/hls.py
@@ -106,7 +106,7 @@ def real_download(self, filename, info_dict):
             if line:
                 if not line.startswith('#'):
                     frag_index += 1
-                    if frag_index <= ctx['frag_index']:
+                    if frag_index <= ctx['fragment_index']:
                         continue
                     frag_url = (
                         line
diff --git a/youtube_dl/downloader/ism.py b/youtube_dl/downloader/ism.py
index 9f0fc36b39..338820e71c 100644
--- a/youtube_dl/downloader/ism.py
+++ b/youtube_dl/downloader/ism.py
@@ -227,7 +227,7 @@ def real_download(self, filename, info_dict):
         frag_index = 0
         for i, segment in enumerate(segments):
             frag_index += 1
-            if frag_index <= ctx['frag_index']:
+            if frag_index <= ctx['fragment_index']:
                 continue
             count = 0
             while count <= fragment_retries: