diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -2474,10 +2474,20 @@ def sort(repo, subset, x, order):
         return revs
     elif keyflags[0][0] == b"topo":
         firstbranch = ()
+        parentrevs = repo.changelog.parentrevs
+        parentsfunc = parentrevs
+        if wdirrev in revs:
+
+            def parentsfunc(r):
+                try:
+                    return parentrevs(r)
+                except error.WdirUnsupported:
+                    return [p.rev() for p in repo[None].parents()]
+
         if b'topo.firstbranch' in opts:
             firstbranch = getset(repo, subset, opts[b'topo.firstbranch'])
         revs = baseset(
-            dagop.toposort(revs, repo.changelog.parentrevs, firstbranch),
+            dagop.toposort(revs, parentsfunc, firstbranch),
             istopo=True,
         )
         if keyflags[0][1]:
diff --git a/tests/test-revset2.t b/tests/test-revset2.t
--- a/tests/test-revset2.t
+++ b/tests/test-revset2.t
@@ -1487,6 +1487,13 @@ prepare repository that has "default" br
   -1
   $ log 'roots(wdir())'
   2147483647
+  $ log 'sort(., -topo)'
+  -1
+  $ log 'sort(. or wdir(), -topo)'
+  -1
+  2147483647
+  $ log 'sort(wdir(), -topo)'
+  2147483647
 
   $ echo default0 >> a
   $ hg ci -Aqm0
@@ -1509,6 +1516,12 @@ prepare repository that has "default" br
   5
   $ log 'roots(wdir())'
   2147483647
+  $ log 'sort(. or wdir() or .^, -topo)'
+  4
+  5
+  2147483647
+  $ log 'sort(wdir(), -topo)'
+  2147483647
 
 "null" revision belongs to "default" branch (issue4683)