diff --git a/hgext/largefiles/uisetup.py b/hgext/largefiles/uisetup.py
--- a/hgext/largefiles/uisetup.py
+++ b/hgext/largefiles/uisetup.py
@@ -175,6 +175,7 @@
 
     # ... and wrap some existing ones
     wireproto.commands['heads'].func = proto.heads
+    # TODO also wrap wireproto.commandsv2 once heads is implemented there.
 
     extensions.wrapfunction(webcommands, 'decodepath', overrides.decodepath)
 
diff --git a/mercurial/wireproto.py b/mercurial/wireproto.py
--- a/mercurial/wireproto.py
+++ b/mercurial/wireproto.py
@@ -502,7 +502,11 @@
 
 def dispatch(repo, proto, command):
     repo = getdispatchrepo(repo, proto, command)
-    func, spec = commands[command]
+
+    transportversion = wireprototypes.TRANSPORTS[proto.name]['version']
+    commandtable = commandsv2 if transportversion == 2 else commands
+    func, spec = commandtable[command]
+
     args = proto.getargs(spec)
     return func(repo, proto, *args)
 
@@ -679,8 +683,12 @@
 POLICY_V1_ONLY = 'v1-only'
 POLICY_V2_ONLY = 'v2-only'
 
+# For version 1 transports.
 commands = commanddict()
 
+# For version 2 transports.
+commandsv2 = commanddict()
+
 def wireprotocommand(name, args='', transportpolicy=POLICY_ALL,
                      permission='push'):
     """Decorator to declare a wire protocol command.
@@ -702,12 +710,15 @@
     """
     if transportpolicy == POLICY_ALL:
         transports = set(wireprototypes.TRANSPORTS)
+        transportversions = {1, 2}
     elif transportpolicy == POLICY_V1_ONLY:
         transports = {k for k, v in wireprototypes.TRANSPORTS.items()
                       if v['version'] == 1}
+        transportversions = {1}
     elif transportpolicy == POLICY_V2_ONLY:
         transports = {k for k, v in wireprototypes.TRANSPORTS.items()
                       if v['version'] == 2}
+        transportversions = {2}
     else:
         raise error.ProgrammingError('invalid transport policy value: %s' %
                                      transportpolicy)
@@ -724,8 +735,21 @@
                                      permission)
 
     def register(func):
-        commands[name] = commandentry(func, args=args, transports=transports,
-                                      permission=permission)
+        if 1 in transportversions:
+            if name in commands:
+                raise error.ProgrammingError('%s command already registered '
+                                             'for version 1' % name)
+            commands[name] = commandentry(func, args=args,
+                                          transports=transports,
+                                          permission=permission)
+        if 2 in transportversions:
+            if name in commandsv2:
+                raise error.ProgrammingError('%s command already registered '
+                                             'for version 2' % name)
+            commandsv2[name] = commandentry(func, args=args,
+                                            transports=transports,
+                                            permission=permission)
+
         return func
     return register
 
diff --git a/mercurial/wireprotoserver.py b/mercurial/wireprotoserver.py
--- a/mercurial/wireprotoserver.py
+++ b/mercurial/wireprotoserver.py
@@ -335,7 +335,7 @@
     # extension.
     extracommands = {'multirequest'}
 
-    if command not in wireproto.commands and command not in extracommands:
+    if command not in wireproto.commandsv2 and command not in extracommands:
         res.status = b'404 Not Found'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('unknown wire protocol command: %s\n') % command)
@@ -346,7 +346,7 @@
 
     proto = httpv2protocolhandler(req, ui)
 
-    if (not wireproto.commands.commandavailable(command, proto)
+    if (not wireproto.commandsv2.commandavailable(command, proto)
         and command not in extracommands):
         res.status = b'404 Not Found'
         res.headers[b'Content-Type'] = b'text/plain'
@@ -502,7 +502,7 @@
     proto = httpv2protocolhandler(req, ui, args=command['args'])
 
     if reqcommand == b'multirequest':
-        if not wireproto.commands.commandavailable(command['command'], proto):
+        if not wireproto.commandsv2.commandavailable(command['command'], proto):
             # TODO proper error mechanism
             res.status = b'200 OK'
             res.headers[b'Content-Type'] = b'text/plain'
@@ -512,7 +512,7 @@
 
         # TODO don't use assert here, since it may be elided by -O.
         assert authedperm in (b'ro', b'rw')
-        wirecommand = wireproto.commands[command['command']]
+        wirecommand = wireproto.commandsv2[command['command']]
         assert wirecommand.permission in ('push', 'pull')
 
         if authedperm == b'ro' and wirecommand.permission != 'pull':
diff --git a/tests/test-wireproto.py b/tests/test-wireproto.py
--- a/tests/test-wireproto.py
+++ b/tests/test-wireproto.py
@@ -13,6 +13,8 @@
 class proto(object):
     def __init__(self, args):
         self.args = args
+        self.name = 'dummyproto'
+
     def getargs(self, spec):
         args = self.args
         args.setdefault(b'*', {})
@@ -22,6 +24,11 @@
     def checkperm(self, perm):
         pass
 
+wireprototypes.TRANSPORTS['dummyproto'] = {
+    'transport': 'dummy',
+    'version': 1,
+}
+
 class clientpeer(wireproto.wirepeer):
     def __init__(self, serverrepo, ui):
         self.serverrepo = serverrepo