diff --git a/asv/plugins/git.py b/asv/plugins/git.py
index 9323cb7d9..8f01971ca 100644
--- a/asv/plugins/git.py
+++ b/asv/plugins/git.py
@@ -66,8 +66,8 @@ def _run_git(self, args, cwd=True, **kwargs):
         kwargs['cwd'] = cwd
         env = dict(kwargs.pop('env', os.environ))
         if cwd is not None:
-            env['GIT_CEILING_DIRECTORIES'] = ':'.join([
-                os.path.join(cwd, os.pardir),
+            env['GIT_CEILING_DIRECTORIES'] = os.pathsep.join([
+                os.path.join(os.path.abspath(cwd), os.pardir),
                 env.get('GIT_CEILING_DIRECTORIES', '')])
         return util.check_output([self._git] + args, env=env, **kwargs)