diff --git a/hggit/__init__.py b/hggit/__init__.py
index 1fec6463922bba1193f3637b071bda88f2786cac_aGdnaXQvX19pbml0X18ucHk=..9c15c89088fd57212a19e969d8de66491b66c974_aGdnaXQvX19pbml0X18ucHk= 100644
--- a/hggit/__init__.py
+++ b/hggit/__init__.py
@@ -208,7 +208,9 @@
     if not isinstance(repo, gitrepo.gitrepo):
 
         if (getattr(dirstate, 'rootcache', False) and
-            (not ignoremod or getattr(ignore, 'readpats', False))):
+            (not ignoremod or getattr(ignore, 'readpats', False)) and
+            hgutil.safehasattr(repo, 'join') and
+            os.path.exists(repo.join('git'))):
             # only install our dirstate wrapper if it has a hope of working
             import gitdirstate
             if ignoremod:
diff --git a/tests/test-gitignore.t b/tests/test-gitignore.t
index 1fec6463922bba1193f3637b071bda88f2786cac_dGVzdHMvdGVzdC1naXRpZ25vcmUudA==..9c15c89088fd57212a19e969d8de66491b66c974_dGVzdHMvdGVzdC1naXRpZ25vcmUudA== 100644
--- a/tests/test-gitignore.t
+++ b/tests/test-gitignore.t
@@ -5,6 +5,11 @@
 
   $ hg init
 
+We should only read .gitignore files in a hg-git repo (i.e. one with .hg/git
+directory) otherwise, a rogue .gitignore could slow down a hg-only repo
+
+  $ mkdir .hg/git
+
   $ touch foo
   $ touch foobar
   $ touch bar