--- a/python/mozbuild/mozbuild/virtualenv.py
+++ b/python/mozbuild/mozbuild/virtualenv.py
@@ -11,16 +11,19 @@ import distutils.sysconfig
 import os
 import shutil
 import subprocess
 import sys
 import warnings
 
 from distutils.version import LooseVersion
 
+IS_NATIVE_WIN = (sys.platform == 'win32' and os.sep == '\\')
+IS_MSYS2 = (sys.platform == 'win32' and os.sep == '/')
+IS_CYGWIN = (sys.platform == 'cygwin')
 
 # Minimum version of Python required to build.
 MINIMUM_PYTHON_VERSION = LooseVersion('2.7.3')
 MINIMUM_PYTHON_MAJOR = 2
 
 
 UPGRADE_WINDOWS = '''
 Please upgrade to the latest MozillaBuild development environment. See
@@ -67,17 +70,17 @@ class VirtualenvManager(object):
             'virtualenv.py')
 
     @property
     def bin_path(self):
         # virtualenv.py provides a similar API via path_locations(). However,
         # we have a bit of a chicken-and-egg problem and can't reliably
         # import virtualenv. The functionality is trivial, so just implement
         # it here.
-        if sys.platform in ('win32', 'cygwin'):
+        if IS_CYGWIN or IS_NATIVE_WIN:
             return os.path.join(self.virtualenv_root, 'Scripts')
 
         return os.path.join(self.virtualenv_root, 'bin')
 
     @property
     def python_path(self):
         binary = 'python'
         if sys.platform in ('win32', 'cygwin'):