diff --git a/swh/loader/tar/utils.py b/swh/loader/tar/utils.py
index 4f5d9db..b4ea451 100644
--- a/swh/loader/tar/utils.py
+++ b/swh/loader/tar/utils.py
@@ -1,127 +1,127 @@
 # Copyright (C) 2015  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import re
 
 from swh.core import hashutil
 
 
 # FIXME; extract this in property
 # to recognize existing naming pattern
 extensions = [
     'ps',
     'zip',
     'tar',
     'gz', 'tgz',
     'bz2', 'bzip2',
     'lzma', 'lz',
     'xz',
     'Z',
     'diff',
     'iso',
     'exe',
     'jar',
     'egg',
     'gem',
     'xpi',
     'apk',
     'dmg',
     'DevPak',
 ]
 
 
 pattern = re.compile(r'''
 ^
 (?:
     # We have a software name and a release number, separated with a
     # -, _ or dot.
     (?P<software_name1>.+?[-_.])
     (?P<release_number>[0-9][0-9a-zA-Z_.+:~-]*?)
 |
     # We couldn't match a release number, put everything in the
     # software name.
     (?P<software_name2>.+?)
 )
 (?P<extension>(?:\.(?:%s))+)
 $
 ''' % '|'.join(extensions),
      flags=re.VERBOSE)
 
 
 def parse_filename(filename):
     """Parse a filename into its components.
 
     Parsing policy:
     We use Debian's release number heuristic: A release number starts
     with a digit, and is followed by alphanumeric characters or any of
     ., +, :, ~ and -
 
     We hardcode a list of possible extensions, as this release number
     scheme would match them too... We match on any combination of those.
 
     Greedy matching is done right to left (we only match the extension
     greedily with +, software_name and release_number are matched lazily
     with +? and *?).
 
     Args:
         filename: filename without path.
 
     Returns:
         Dictionary with the following keys:
         - software_name
         - release_number: can be None if it could not be found.
         - extension
 
     Raises:
         ValueError if the filename could not be parsed.
 
 """
     m = pattern.match(filename)
     if not m:
         raise ValueError('Filename %s could not be parsed.' % filename)
 
     d = m.groupdict()
     return {
         'software_name': d['software_name1'] or d['software_name2'],
         'release_number': d['release_number'],
         'extension': d['extension'],
     }
 
 
 def release_number(filename):
     """Compute the release number from the filename.
 
     cf. parse_filename's docstring
 
     """
     return parse_filename(filename)['release_number']
 
 
 def commonname(path0, path1, as_str=False):
     """Compute the commonname between the path0 and path1.
 
     """
     return path1.split(path0)[1]
 
 
 def convert_to_hex(d):
     """Convert a flat dictionary with bytes in values to the same dictionary
     with hex as values.
 
     Args:
         dict: flat dictionary with sha bytes in their values.
 
     Returns:
         Mirror dictionary with values as string hex.
 
     """
     if not d:
         return d
 
     checksums = {}
-    for key_hash in d:
-        checksums[key_hash] = hashutil.hash_to_hex(d[key_hash])
+    for key, h in d.items():
+        checksums[key] = hashutil.hash_to_hex(h)
 
     return checksums