diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -1351,6 +1351,8 @@ def rev(repo, subset, x):
     except (TypeError, ValueError):
         # i18n: "rev" is a keyword
         raise error.ParseError(_("rev expects a number"))
+    if l not in repo.changelog:
+        return baseset()
     return subset & baseset([l])
 
 def matching(repo, subset, x):
diff --git a/tests/test-obsolete.t b/tests/test-obsolete.t
--- a/tests/test-obsolete.t
+++ b/tests/test-obsolete.t
@@ -185,6 +185,8 @@ check that various commands work well wi
   abort: hidden revision '4'!
   (use --hidden to access hidden revisions)
   [255]
+  $ hg debugrevspec 'rev(6)'
+  $ hg debugrevspec 'rev(4)'
 
 Check that public changeset are not accounted as obsolete:
 
diff --git a/tests/test-revset.t b/tests/test-revset.t
--- a/tests/test-revset.t
+++ b/tests/test-revset.t
@@ -437,6 +437,18 @@ Test empty set input
   4
   8
   9
+
+Test explicit numeric revision
+  $ log 'rev(-1)'
+  $ log 'rev(0)'
+  0
+  $ log 'rev(9)'
+  9
+  $ log 'rev(10)'
+  $ log 'rev(tip)'
+  hg: parse error: rev expects a number
+  [255]
+
   $ log 'outgoing()'
   8
   9