diff --git a/lib/cli.py b/lib/cli.py
index 826000e..170763d 100644
--- a/lib/cli.py
+++ b/lib/cli.py
@@ -73,7 +73,7 @@ def get_slice_repr(lst):
     def fold(lst, obj):
         return lst + [obj - sum(lst)]
     plus_lst = functools.reduce(fold, lst[1:], lst[:1])
-    return '+'.join(map(str, plus_lst))
+    return str.join('+', map(str, plus_lst))
 
 class intact(object):
 
@@ -344,11 +344,11 @@ def dump_options(o, multipage=False):
     method_name = o.method.name
     if o.params:
         method_name += ' '
-        method_name += ' '.join(
+        method_name += str.join(' ', (
             '{0}={1}'.format(pname, pvalue)
             for pname, pvalue
             in sorted(o.params.iteritems())
-        )
+        ))
     yield ('method', method_name)
     if multipage:
         yield ('pages-per-dict', o.pages_per_dict)
diff --git a/lib/djvu_support.py b/lib/djvu_support.py
index d32573b..1f82f7e 100644
--- a/lib/djvu_support.py
+++ b/lib/djvu_support.py
@@ -89,7 +89,7 @@ def photo_to_djvu(image, dpi=100, slices=IW44_SLICES_DEFAULT, gamma=2.2, mask_im
         args = [
             'c44',
             '-dpi', str(dpi),
-            '-slice', ','.join(map(str, slices)),
+            '-slice', str.join(',', map(str, slices)),
             '-gamma', '{0:.1f}'.format(gamma),
             '-crcb{0}'.format(crcb),
         ]
diff --git a/lib/ipc.py b/lib/ipc.py
index 7f897fd..d24d6ed 100644
--- a/lib/ipc.py
+++ b/lib/ipc.py
@@ -70,7 +70,7 @@ def __str__(self):
 # ==========
 
 def shell_escape(commandline):
-    return ' '.join(map(pipes.quote, commandline))
+    return str.join(' ', map(pipes.quote, commandline))
 
 class Subprocess(subprocess.Popen):
 
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 6ab1fb1..0ba6226 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -193,7 +193,7 @@ def test_no_args(self):
         assert_multi_line_equal(
             stderr.getvalue(),
             'usage: didjvu [-h] [--version] {{{actions}}} ...\n'
-            'didjvu: error: too few arguments\n'.format(actions=','.join(self.anames))
+            'didjvu: error: too few arguments\n'.format(actions=str.join(',', self.anames))
         )
 
     def _test_action_no_args(self, action):
diff --git a/tests/test_ipc.py b/tests/test_ipc.py
index a154cff..b125a97 100644
--- a/tests/test_ipc.py
+++ b/tests/test_ipc.py
@@ -158,7 +158,7 @@ def _test_locale(self):
                 if utf8_locale is None:
                     raise SkipTest(
                         'UTF-8 locale missing '
-                        '({0})'.format(' or '.join(utf8_locale_candidates))
+                        '({0})'.format(str.join(' or ', utf8_locale_candidates))
                     )
                 assert_equal(value, utf8_locale)
             elif key == 'LANG':
diff --git a/tests/tools.py b/tests/tools.py
index 6dae01a..a4ab5d0 100644
--- a/tests/tools.py
+++ b/tests/tools.py
@@ -135,7 +135,7 @@ def wrapper(*args, **kwargs):
             except Exception:
                 exctp, exc, tb = sys.exc_info()
                 s = traceback.format_exception(exctp, exc, tb, _n_relevant_tb_levels(tb))
-                s = ''.join(s)
+                s = str.join('', s)
                 del tb
                 with os.fdopen(writefd, 'wb') as fp:
                     fp.write(s)