diff --git a/hggit/overlay.py b/hggit/overlay.py
index da01212cd53a11fa477b21924da5360e466cf9cd_aGdnaXQvb3ZlcmxheS5weQ==..517cf1b5e6269db897895309e7060f798cbb7907_aGdnaXQvb3ZlcmxheS5weQ== 100644
--- a/hggit/overlay.py
+++ b/hggit/overlay.py
@@ -190,7 +190,10 @@
         return self.commit.message
 
     def parents(self):
-        return [overlaychangectx(self.repo, sha) for sha in self.commit.parents]
+        parents = self.commit.parents
+        if not parents:
+            return [self.repo['null']]
+        return [overlaychangectx(self.repo, sha) for sha in parents]
 
     def manifestnode(self):
         return bin(self.commit.tree)