diff --git a/hgext3rd/undo.py b/hgext3rd/undo.py
--- a/hgext3rd/undo.py
+++ b/hgext3rd/undo.py
@@ -6,7 +6,7 @@
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
-import os
+import weakref
 
 from mercurial.i18n import _
 
@@ -19,6 +19,7 @@
     revset,
     revsetlang,
     smartset,
+    transaction,
     util,
 )
 
@@ -31,6 +32,11 @@
 cmdtable = {}
 command = registrar.command(cmdtable)
 
+# Setup
+
+def extsetup(ui):
+    extensions.wrapfunction(dispatch, 'runcommand', _runcommandwrapper)
+
 # Wrappers
 
 def _runcommandwrapper(orig, lui, repo, cmd, fullargs, *args):
@@ -42,7 +48,7 @@
     # Check wether undolog is consistent
     # ie check wether the undo ext was
     # off before this command
-    safelog(repo, "")
+    safelog(repo, [""])
 
     result = orig(lui, repo, cmd, fullargs, *args)
 
@@ -53,10 +59,23 @@
 # Write: Log control
 
 def safelog(repo, command):
+    changes = False
     if repo is not None:# some hg commands don't require repo
         with repo.lock():
-            with repo.transaction("undolog"):
-                log(repo.filtered('visible'), command)
+            with lighttransaction(repo):
+                changes = log(repo.filtered('visible'), command)
+    return changes
+
+def lighttransaction(repo):
+    # full fledged transactions have two serious issues:
+    # 1. they may cause infite loops through hooks
+    #    that run commands
+    # 2. they are really expensive performance wise
+    vfsmap = {'plain': repo.vfs}
+    tr = transaction.transaction(repo.ui.warn, repo.svfs, vfsmap,
+                                 "_undojournal", "_undolog")
+    repo._transref = weakref.ref(tr)
+    return tr
 
 def log(repo, command):
     newnodes = {
@@ -69,24 +88,24 @@
     except IndexError:
         exsistingnodes = {}
     if all(newnodes.get(x) == exsistingnodes.get(x) for x in newnodes.keys()):
-        return
+        return False
     else:
         newnodes.update({
             'date': _logdate(repo),
             'command': _logcommand(repo, command),
         })
         _logindex(repo, newnodes)
+        return True
 
 # Write: Logs
 
 def writelog(repo, name, revstring):
-    assert repo.currenttransaction() is not None
-    # The transaction code doesn't work with vfs
+    tr = repo.currenttransaction()
+    assert tr is not None
+    # the transaction code doesn't work with vfs
     # specifically, repo.recover() assumes svfs?
     repo.svfs.makedirs('undolog')
-    path = os.path.join('undolog', name)
-    rlog = revlog.revlog(repo.svfs, path)
-    tr = repo.currenttransaction()
+    rlog = _getrevlog(repo, name)
     node = rlog.addrevision(revstring, tr, 1, nullid, nullid)
     return hex(node)
 
@@ -122,11 +141,10 @@
 
 def _readindex(repo, reverseindex, prefetchedrevlog=None):
     if prefetchedrevlog is None:
-        path = os.path.join('undolog', 'index.i')
-        rlog = revlog.revlog(repo.svfs, path)
+        rlog = _getrevlog(repo, 'index.i')
     else:
         rlog = prefetchedrevlog
-    index = len(rlog) - reverseindex - 1
+    index = _invertindex(rlog, reverseindex)
     if index < 0 or index > len(rlog) - 1:
         raise IndexError
     chunk = rlog.revision(index)
@@ -138,8 +156,7 @@
     return indexdict
 
 def _readnode(repo, filename, hexnode):
-    path = os.path.join('undolog', filename)
-    rlog = revlog.revlog(repo.svfs, path)
+    rlog = _getrevlog(repo, filename)
     return rlog.revision(bin(hexnode))
 
 # Visualize
@@ -154,19 +171,19 @@
     ('n', 'index', 0, _("details about specific operation")),
     ('l', 'list', False, _("list recent undo-able operation"))
 ])
-def debugundohistory(ui, repo, *args, **kwargs):
+def debugundohistory(ui, repo, *args, **opts):
     """ Print operational history
         0 is the most recent operation
     """
     if repo is not None:
-        if kwargs.get('list'):
+        if opts.get('list'):
             if args and args[0].isdigit():
                 offset = int(args[0])
             else:
                 offset = 0
             _debugundolist(ui, repo, offset)
         else:
-            reverseindex = kwargs.get('index')
+            reverseindex = opts.get('index')
             if 0 == reverseindex and args and args[0].isdigit():
                 reverseindex = int(args[0])
             _debugundoindex(ui, repo, reverseindex)
@@ -176,9 +193,7 @@
 
     template = "{sub('\0', ' ', undo)}\n"
     fm = ui.formatter('debugundohistory', {'template': template})
-    path = os.path.join('undolog', 'index.i')
-
-    prefetchedrevlog = revlog.revlog(repo.svfs, path)
+    prefetchedrevlog = _getrevlog(repo, 'index.i')
     recentrange = min(5, len(prefetchedrevlog) - offset)
     if 0 == recentrange:
         fm.startitem()
@@ -186,6 +201,8 @@
     for i in range(recentrange):
         nodedict = _readindex(repo, i + offset, prefetchedrevlog)
         commandstr = _readnode(repo, 'command.i', nodedict['command'])
+        if "" == commandstr:
+            commandstr = " -- gap in log -- "
         fm.startitem()
         fm.write('undo', '%s', str(i + offset) + ": " + commandstr)
     fm.end()
@@ -211,7 +228,7 @@
             try:
                 oldnodes = _readindex(repo, reverseindex + 1)
                 oldheads = _readnode(repo, filename, oldnodes[filename[:-2]])
-            except IndexError:# Index is oldest log
+            except IndexError:# index is oldest log
                 content = rawcontent
             else:
                 content = "ADDED:\n\t" + "\n\t".join(sorted(
@@ -259,7 +276,11 @@
     revs = _getolddrafts(repo, reverseindex)
     return smartset.baseset(revs)
 
-# Setup
+# Tools
 
-def extsetup(ui):
-    extensions.wrapfunction(dispatch, 'runcommand', _runcommandwrapper)
+def _invertindex(rlog, indexorreverseindex):
+    return len(rlog) - 1 - indexorreverseindex
+
+def _getrevlog(repo, filename):
+    path = 'undolog/' + filename
+    return revlog.revlog(repo.svfs, path)
diff --git a/tests/test-undo.t b/tests/test-undo.t
--- a/tests/test-undo.t
+++ b/tests/test-undo.t
@@ -121,7 +121,7 @@
   $ touch a5 && hg add a5 && hg ci -ma5
   $ hg debugundohistory -l
   0: ci -ma5
-  1: 
+  1:  -- gap in log -- 
   2: commit -m words
   3: update master
   4: commit --amend
@@ -148,7 +148,8 @@
   [255]
 
 Revset tests
-  $ hg log -G -r 'draft()' --hidden >> c1
+  $ hg log -G -r 'draft()' --hidden | head -1
+  @  changeset:   8:aa430c8afedf
   $ hg debugundohistory -n 0
   command:
   	ci -ma5