diff -r 5bfab9400daf -r 481db51c83e9 mercurial/dirstate.py
--- a/mercurial/dirstate.py	Tue Sep 04 10:22:42 2018 -0700
+++ b/mercurial/dirstate.py	Wed Sep 05 09:36:31 2018 -0700
@@ -1405,9 +1405,9 @@
 
             l = len(st)
             if l == 40:
-                self._parents = st[:20], st[20:40]
+                self._parents = (st[:20], st[20:40])
             elif l == 0:
-                self._parents = [nullid, nullid]
+                self._parents = (nullid, nullid)
             else:
                 raise error.Abort(_('working directory state appears '
                                     'damaged!'))