diff --git a/youtube_dl/extractor/generic.py b/youtube_dl/extractor/generic.py
index acdf725cc..b4f748e87 100644
--- a/youtube_dl/extractor/generic.py
+++ b/youtube_dl/extractor/generic.py
@@ -12,6 +12,7 @@ from ..utils import (
     compat_urlparse,
     compat_xml_parse_error,
 
+    determine_ext,
     ExtractorError,
     float_or_none,
     HEADRequest,
diff --git a/youtube_dl/extractor/musicvault.py b/youtube_dl/extractor/musicvault.py
index 329bf61e0..ebb1eb8e9 100644
--- a/youtube_dl/extractor/musicvault.py
+++ b/youtube_dl/extractor/musicvault.py
@@ -1,11 +1,9 @@
 from __future__ import unicode_literals
 
-import json
 import re
 
 from .common import InfoExtractor
 from ..utils import (
-    strip_jsonp,
     parse_duration,
     unified_strdate,
 )
diff --git a/youtube_dl/extractor/ustream.py b/youtube_dl/extractor/ustream.py
index 816b101eb..994b60a76 100644
--- a/youtube_dl/extractor/ustream.py
+++ b/youtube_dl/extractor/ustream.py
@@ -1,6 +1,5 @@
 from __future__ import unicode_literals
 
-import json
 import re
 
 from .common import InfoExtractor