diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -632,7 +632,10 @@ def commonancestors(repo, subset, x):
 
     """
     # only wants the heads of the set passed in
-    for r in heads(repo, fullreposet(repo), x, anyorder):
+    h = heads(repo, fullreposet(repo), x, anyorder)
+    if not h:
+        return baseset()
+    for r in h:
         subset &= dagop.revancestors(repo, baseset([r]))
 
     return subset
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -1063,6 +1063,12 @@ test common ancestors
   8
   9
 
+test ancestor variants of empty revision
+
+  $ log 'ancestor(none())'
+  $ log 'ancestors(none())'
+  $ log 'commonancestors(none())'
+
 test ancestors with depth limit
 
  (depth=0 selects the node itself)