--- a/hgsubversion/help/subversion.rst
+++ b/hgsubversion/help/subversion.rst
@@ -162,6 +162,10 @@ settings:
 
       joe = Joe User <joe@example.com>
 
+    Some Subversion conversion tools create revisions without
+    specifying an author.  Such author names are mapped to ``(no
+    author)``, similar to how ``svn log`` will display them.
+
   hgsubversion.defaulthost
     This option specifies the hostname to append to unmapped Subversion
     usernames. The default is to append the UUID of the Subversion repository

--- a/hgsubversion/maps.py
+++ b/hgsubversion/maps.py
@@ -76,6 +76,8 @@ class AuthorMap(dict):
         ''' Similar to dict.__getitem__, except in case of an unknown author.
         In such cases, a new value is generated and added to the dictionary
         as well as the backing store. '''
+        if author is None:
+            author = '(no author)'
         if author in self:
             result = self.super.__getitem__(author)
         elif self.ui.configbool('hgsubversion', 'defaultauthors', True):

--- a/hgsubversion/svncommands.py
+++ b/hgsubversion/svncommands.py
@@ -418,7 +418,10 @@ def listauthors(ui, args, authors=None, 
     svn = svnrepo.svnremoterepo(ui, args[0]).svn
     author_set = set()
     for rev in svn.revisions():
-        author_set.add(str(rev.author)) # So None becomes 'None'
+        if rev.author is None:
+            author_set.add('(no author)')
+        else:
+            author_set.add(rev.author)
     if authors:
         authorfile = open(authors, 'w')
         authorfile.write('%s=\n' % '=\n'.join(sorted(author_set)))

new file mode 100644
--- /dev/null
+++ b/tests/fixtures/no-author.svndump
@@ -0,0 +1,82 @@
+SVN-fs-dump-format-version: 2
+
+UUID: df2126f7-00ab-4d49-b42c-7e981dde0bcf
+
+Revision-number: 0
+Prop-content-length: 56
+Content-length: 56
+
+K 8
+svn:date
+V 27
+2008-10-07T22:49:12.059692Z
+PROPS-END
+
+Revision-number: 1
+Prop-content-length: 85
+Content-length: 85
+
+K 7
+svn:log
+V 11
+Empty dirs.
+K 8
+svn:date
+V 27
+2008-10-07T22:49:41.118037Z
+PROPS-END
+
+Node-path: branches
+Node-kind: dir
+Node-action: add
+Prop-content-length: 10
+Content-length: 10
+
+PROPS-END
+
+
+Node-path: tags
+Node-kind: dir
+Node-action: add
+Prop-content-length: 10
+Content-length: 10
+
+PROPS-END
+
+
+Node-path: trunk
+Node-kind: dir
+Node-action: add
+Prop-content-length: 10
+Content-length: 10
+
+PROPS-END
+
+
+Revision-number: 2
+Prop-content-length: 82
+Content-length: 82
+
+K 7
+svn:log
+V 9
+Add alpha
+K 8
+svn:date
+V 27
+2008-10-07T23:23:02.991743Z
+PROPS-END
+
+Node-path: trunk/alpha
+Node-kind: file
+Node-action: add
+Prop-content-length: 10
+Text-content-length: 12
+Text-content-md5: 3c72ebf8bbd7fa88b1fdcee5398b5a17
+Text-content-sha1: f552a50b53177d35b29a4a0ab1cece918b5b5e9b
+Content-length: 22
+
+PROPS-END
+file: alpha
+
+

--- a/tests/test_fetch_mappings.py
+++ b/tests/test_fetch_mappings.py
@@ -65,6 +65,27 @@ class MapTests(test_util.TestBase):
     def test_author_map_closing_author_stupid(self):
         self.test_author_map_closing_author(True)
 
+    def test_author_map_no_author(self, stupid=False):
+        self._load_fixture_and_fetch('no-author.svndump')
+        users = set(self.repo[r].user() for r in self.repo)
+        expected_users = ['(no author)@%s' % self.repo.svnmeta().uuid]
+        self.assertEqual(sorted(users), expected_users)
+        test_util.rmtree(self.wc_path)
+
+        authormap = open(self.authors, 'w')
+        authormap.write("(no author)=Testy <test@example.com>")
+        authormap.close()
+        ui = self.ui(stupid)
+        ui.setconfig('hgsubversion', 'authormap', self.authors)
+        commands.clone(ui, test_util.fileurl(self.repo_path),
+                       self.wc_path, authors=self.authors)
+        users = set(self.repo[r].user() for r in self.repo)
+        expected_users = ['Testy <test@example.com>']
+        self.assertEqual(sorted(users), expected_users)
+
+    def test_author_map_no_author_stupid(self):
+        self.test_author_map_no_author(True)
+
     def test_author_map_no_overwrite(self):
         cwd = os.path.dirname(__file__)
         orig = os.path.join(cwd, 'fixtures', 'author-map-test.txt')

--- a/tests/test_push_command.py
+++ b/tests/test_push_command.py
@@ -131,7 +131,7 @@ class PushTests(test_util.TestBase):
             self.assertEqual(tip.branch(), 'default')
             # unintended behaviour:
             self.assertNotEqual('an_author', tip.user())
-            self.assertEqual('None', tip.user().rsplit('@', 1)[0])
+            self.assertEqual('(no author)', tip.user().rsplit('@', 1)[0])
         finally:
             # TODO: use svnserve.kill() in Python >2.5
             test_util.kill_process(svnserve)