diff --git a/mercurial/phases.py b/mercurial/phases.py
index 98cc121099fe8b03cf0e5c4c76306b47b1419bc6_bWVyY3VyaWFsL3BoYXNlcy5weQ==..56745e58df070d15034685c9c63745a1bfc25464_bWVyY3VyaWFsL3BoYXNlcy5weQ== 100644
--- a/mercurial/phases.py
+++ b/mercurial/phases.py
@@ -203,7 +203,7 @@
         if _load:
             # Cheap trick to allow shallow-copy without copy module
             self.phaseroots, self.dirty = _readroots(repo, phasedefaults)
-            self._loadedrevslen = nullrev
+            self._loadedrevslen = 0
             self._phasesets = None
             self.filterunknown(repo)
             self.opener = repo.svfs
@@ -294,7 +294,7 @@
                 self._computephaserevspure(repo)
 
     def invalidate(self):
-        self._loadedrevslen = nullrev
+        self._loadedrevslen = 0
         self._phasesets = None
 
     def phase(self, repo, rev):