--- a/mercurial/phases.py	Fri Aug 24 10:19:31 2018 -0700
+++ b/mercurial/phases.py	Fri Aug 24 12:55:05 2018 -0700
@@ -673,13 +673,11 @@
     rev = cl.nodemap.get
     if not roots:
         return heads
-    if not heads or heads == [nullrev]:
+    if not heads or heads == [nullid]:
         return []
     # The logic operated on revisions, convert arguments early for convenience
     new_heads = set(rev(n) for n in heads if n != nullid)
     roots = [rev(n) for n in roots]
-    if not heads or not roots:
-        return heads
     # compute the area we need to remove
     affected_zone = repo.revs("(%ld::%ld)", roots, new_heads)
     # heads in the area are no longer heads