diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -520,10 +520,12 @@ def bisect(ui, repo, rev=None, extra=Non
     revision as good or bad without checking it out first.
 
     If you supply a command, it will be used for automatic bisection.
-    Its exit status will be used to mark revisions as good or bad:
-    status 0 means good, 125 means to skip the revision, 127
-    (command not found) will abort the bisection, and any other
-    non-zero exit status means the revision is bad.
+    The environment variable HG_NODE will contain the ID of the
+    changeset being tested. The exit status of the command will be
+    used to mark revisions as good or bad: status 0 means good, 125
+    means to skip the revision, 127 (command not found) will abort the
+    bisection, and any other non-zero exit status means the revision
+    is bad.
 
     .. container:: verbose
 
@@ -665,7 +667,9 @@ def bisect(ui, repo, rev=None, extra=Non
                 # update state
                 state['current'] = [node]
                 hbisect.save_state(repo, state)
-                status = util.system(command, out=ui.fout)
+                status = util.system(command,
+                                     environ={'HG_NODE': hex(node)},
+                                     out=ui.fout)
                 if status == 125:
                     transition = "skip"
                 elif status == 0:
diff --git a/tests/test-bisect.t b/tests/test-bisect.t
--- a/tests/test-bisect.t
+++ b/tests/test-bisect.t
@@ -473,3 +473,40 @@ test bisecting command
   date:        Thu Jan 01 00:00:06 1970 +0000
   summary:     msg 6
   
+
+
+test bisecting via a command without updating the working dir, and
+ensure that the bisect state file is updated before running a test
+command
+
+  $ hg update null
+  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ cat > script.sh <<'EOF'
+  > #!/bin/sh
+  > test -n "$HG_NODE" || (echo HG_NODE missing; exit 127)
+  > current="`hg log -r \"bisect(current)\" --template {node}`"
+  > test "$current" = "$HG_NODE" || (echo current is bad: $current; exit 127)
+  > rev="`hg log -r $HG_NODE --template {rev}`"
+  > test "$rev" -ge 6
+  > EOF
+  $ chmod +x script.sh
+  $ hg bisect -r
+  $ hg bisect --good tip --noupdate
+  $ hg bisect --bad 0 --noupdate
+  Testing changeset 15:e7fa0811edb0 (31 changesets remaining, ~4 tests)
+  $ hg bisect --command "'`pwd`/script.sh' and some params" --noupdate
+  Changeset 15:e7fa0811edb0: good
+  Changeset 7:03750880c6b5: good
+  Changeset 3:b53bea5e2fcb: bad
+  Changeset 5:7874a09ea728: bad
+  Changeset 6:a3d5c6fdf0d3: good
+  The first good revision is:
+  changeset:   6:a3d5c6fdf0d3
+  user:        test
+  date:        Thu Jan 01 00:00:06 1970 +0000
+  summary:     msg 6
+  
+
+ensure that we still don't have a working dir
+
+  $ hg parents