diff --git a/bindep/depends.py b/bindep/depends.py
index abf91d5..244700d 100644
--- a/bindep/depends.py
+++ b/bindep/depends.py
@@ -658,8 +658,8 @@ def _cmp_segment(l_str, r_str):
     while (r_offset < len(r_str)) or (l_offset < len(l_str)):
         r_char = r_str[r_offset:r_offset + 1]
         l_char = l_str[l_offset:l_offset + 1]
-        if ((not r_char or r_char.isdigit())
-            and (not l_char or l_char.isdigit())):
+        if ((not r_char or r_char.isdigit()) and
+            (not l_char or l_char.isdigit())):
             l_int, l_offset = _find_int(l_str, l_offset)
             r_int, r_offset = _find_int(r_str, r_offset)
             diff = l_int - r_int
diff --git a/test-requirements.txt b/test-requirements.txt
index 21d66a3..acb1c98 100644
--- a/test-requirements.txt
+++ b/test-requirements.txt
@@ -1,4 +1,4 @@
-hacking>=0.10.0,<0.11
+hacking
 
 coverage>=3.6
 fixtures>=0.3.12
@@ -6,6 +6,7 @@ mock>=2.0  # BSD
 python-subunit
 testrepository>=0.0.13
 testtools>=0.9.27
-sphinx>1.6.1  # BSD
+sphinx!=1.6.6,!=1.6.7,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,!=2.1.0;python_version>='3.4'  # BSD
 openstackdocstheme>=1.24.1  # Apache-2.0
 sphinxcontrib-programoutput  # BSD license
diff --git a/tox.ini b/tox.ini
index f037afe..4506c5f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,9 +1,11 @@
 [tox]
 envlist = py35,py27,pypy,pep8
 skipdist = True
+ignore_basepython_conflict=true
 
 [testenv]
 usedevelop = True
+basepython = python3
 install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/test-requirements.txt