--- a/hgext/mq.py	Wed Jun 02 19:39:45 2010 +0200
+++ b/hgext/mq.py	Thu Jun 03 20:40:23 2010 +0200
@@ -2633,17 +2633,17 @@
 
     existing = _getqueues()
 
-    if name not in existing and opts.get('delete'):
-        raise util.Abort(_('cannot delete queue that does not exist'))
-    elif name not in existing and not opts.get('create'):
-        raise util.Abort(_('use --create to create a new queue'))
-
     if opts.get('create'):
+        if name in existing:
+            raise util.Abort(_('queue "%s" already exists') % name)
         if _noqueues():
             _addqueue(_defaultqueue)
         _addqueue(name)
         _setactive(name)
     elif opts.get('delete'):
+        if name not in existing:
+            raise util.Abort(_('cannot delete queue that does not exist'))
+
         current = _getcurrent()
 
         if name == current:
@@ -2657,6 +2657,8 @@
         fh.close()
         util.rename(repo.join('patches.queues.new'), repo.join(_allqueues))
     else:
+        if name not in existing:
+            raise util.Abort(_('use --create to create a new queue'))
         _setactive(name)
 
 def reposetup(ui, repo):

--- a/tests/test-mq-qqueue	Wed Jun 02 19:39:45 2010 +0200
+++ b/tests/test-mq-qqueue	Thu Jun 03 20:40:23 2010 +0200
@@ -28,6 +28,10 @@
 hg qqueue foo
 hg qqueue
 
+echo %% fail creating queue with already existing name
+hg qqueue --create foo
+hg qqueue
+
 echo %% unapplied patches
 hg qun
 echo c > a

--- a/tests/test-mq-qqueue.out	Wed Jun 02 19:39:45 2010 +0200
+++ b/tests/test-mq-qqueue.out	Thu Jun 03 20:40:23 2010 +0200
@@ -12,6 +12,10 @@
 %% switch queue
 foo (active)
 patches
+%% fail creating queue with already existing name
+abort: queue "foo" already exists
+foo (active)
+patches
 %% unapplied patches
 %% fail switching back
 abort: patches applied - cannot set new queue active