diff --git a/hgext/mq.py b/hgext/mq.py
--- a/hgext/mq.py
+++ b/hgext/mq.py
@@ -613,8 +613,7 @@ class queue(object):
                     repo.dirstate.invalidate()
                 raise
         finally:
-            del tr
-            release(lock, wlock)
+            release(tr, lock, wlock)
             self.removeundo(repo)
 
     def _apply(self, repo, series, list=False, update_status=True,
diff --git a/mercurial/localrepo.py b/mercurial/localrepo.py
--- a/mercurial/localrepo.py
+++ b/mercurial/localrepo.py
@@ -971,7 +971,8 @@ class localrepository(repo.repository):
                 self.branchtags()
             return n
         finally:
-            del tr
+            if tr:
+                tr.release()
             lock.release()
 
     def destroyed(self):
@@ -2194,7 +2195,7 @@ class localrepository(repo.repository):
 
             tr.close()
         finally:
-            del tr
+            tr.release()
 
         if changesets > 0:
             # forcefully update the on-disk branch cache
diff --git a/mercurial/transaction.py b/mercurial/transaction.py
--- a/mercurial/transaction.py
+++ b/mercurial/transaction.py
@@ -43,6 +43,7 @@ def _playback(journal, report, opener, e
 class transaction(object):
     def __init__(self, report, opener, journal, after=None, createmode=None):
         self.count = 1
+        self.usages = 1
         self.report = report
         self.opener = opener
         self.after = after
@@ -108,8 +109,16 @@ class transaction(object):
     @active
     def nest(self):
         self.count += 1
+        self.usages += 1
         return self
 
+    def release(self):
+        if self.count > 0:
+            self.usages -= 1
+        # of the transaction scopes are left without being closed, fail
+        if self.count > 0 and self.usages == 0:
+            self._abort()
+
     def running(self):
         return self.count > 0
 
@@ -136,6 +145,7 @@ class transaction(object):
 
     def _abort(self):
         self.count = 0
+        self.usages = 0
         self.file.close()
 
         try: