diff --git a/asv/plugins/git.py b/asv/plugins/git.py
index eae450515..891aaaa13 100644
--- a/asv/plugins/git.py
+++ b/asv/plugins/git.py
@@ -64,7 +64,13 @@ def _run_git(self, args, cwd=True, **kwargs):
         if cwd is True:
             cwd = self._path
         kwargs['cwd'] = cwd
-        return util.check_output([self._git] + args, **kwargs)
+        env = dict(kwargs.pop('env', os.environ))
+        if cwd is not None:
+            prev = env.get('GIT_CEILING_DIRECTORIES')
+            env['GIT_CEILING_DIRECTORIES'] = os.pathsep.join(
+                [os.path.join(os.path.abspath(cwd), os.pardir)]
+                + ([prev] if prev is not None else []))
+        return util.check_output([self._git] + args, env=env, **kwargs)
 
     def get_new_range_spec(self, latest_result, branch=None):
         return '{0}..{1}'.format(latest_result, self.get_branch_name(branch))
diff --git a/asv/util.py b/asv/util.py
index 0108a591c..e1c147a2f 100644
--- a/asv/util.py
+++ b/asv/util.py
@@ -422,6 +422,12 @@ def get_content(header=None):
 
     log.debug("Running '{0}'".format(' '.join(args)))
 
+    if env and WIN and sys.version_info < (3,):
+        # Environment keys and values cannot be unicode
+        def _fix_env(s):
+            return s.encode('mbcs') if isinstance(s, unicode) else s
+        env = {_fix_env(k): _fix_env(v) for k, v in env.items()}
+
     kwargs = dict(shell=shell, env=env, cwd=cwd,
                   stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     if WIN:
diff --git a/test/test_repo.py b/test/test_repo.py
index 974d63282..88a498c20 100644
--- a/test/test_repo.py
+++ b/test/test_repo.py
@@ -397,3 +397,40 @@ def test_git_submodule(tmpdir):
     r.checkout(checkout_dir, commit_hash_5)
     assert os.path.isfile(join(checkout_dir, 'README'))
     assert not os.path.isdir(join(checkout_dir, 'sub1'))
+
+
+@pytest.mark.parametrize('dvcs_type', [
+    "git",
+    pytest.mark.skipif(hglib is None, reason="needs hglib")("hg")
+])
+def test_root_ceiling(dvcs_type, tmpdir):
+    # Check that git/hg does not try to look for repository in parent
+    # directories.
+    tmpdir = six.text_type(tmpdir)
+    dvcs1 = tools.generate_repo_from_ops(tmpdir, dvcs_type, [("commit", 1)])
+    dvcs2 = tools.generate_repo_from_ops(tmpdir, dvcs_type, [("commit", 2)])
+    commit1 = dvcs1.get_branch_hashes()[0]
+    commit2 = dvcs2.get_branch_hashes()[0]
+
+    conf = config.Config()
+    conf.branches = []
+    conf.dvcs = dvcs_type
+    conf.project = join(tmpdir, "repo")
+    conf.repo = dvcs1.path
+
+    r = repo.get_repo(conf)
+
+    # Checkout into a subdir inside another repository
+    workcopy_dir = join(dvcs2.path, "workcopy")
+    r.checkout(workcopy_dir, commit1)
+
+    # Corrupt the checkout
+    for pth in ['.hg', '.git']:
+        pth = os.path.join(workcopy_dir, pth)
+        if os.path.isdir(pth):
+            shutil.rmtree(pth)
+
+    # Operation must fail (commit2 is not in dvcs1), not use the
+    # parent repository
+    with pytest.raises(Exception):
+        r.checkout(workcopy_dir, commit2)
diff --git a/test/test_subprocess.py b/test/test_subprocess.py
index 857dcc7fd..70971b74d 100644
--- a/test/test_subprocess.py
+++ b/test/test_subprocess.py
@@ -4,6 +4,7 @@
 from __future__ import (absolute_import, division, print_function,
                         unicode_literals)
 
+import os
 import sys
 import time
 
@@ -104,6 +105,20 @@ def test_output_timeout():
         assert False, "Expected exception"
 
 
+def test_env():
+    code = r"""
+import os
+print(os.environ['TEST_ASV_FOO'])
+print(os.environ['TEST_ASV_BAR'])
+"""
+    env = os.environ.copy()
+    env['TEST_ASV_FOO'] = 'foo'
+    # Force unicode string on Python 2
+    env['TEST_ASV_BAR'] = u'bar'
+    output = util.check_output([sys.executable, "-c", code], env=env)
+    assert output.splitlines() == ['foo', 'bar']
+
+
 # This *does* seem to work, only seems untestable somehow...
 # def test_dots(capsys):
 #     code = r"""