diff --git a/aiohttp/web.py b/aiohttp/web.py
index d2457a626f1..0f95f7aee93 100644
--- a/aiohttp/web.py
+++ b/aiohttp/web.py
@@ -18,6 +18,7 @@
 from .web_reqrep import *  # noqa
 from .web_server import Server
 from .web_urldispatcher import *  # noqa
+from .web_urldispatcher import PrefixedSubAppResource, _wrap_add_subbapp
 from .web_ws import *  # noqa
 
 __all__ = (web_reqrep.__all__ +
@@ -39,7 +40,7 @@ def __init__(self, *, logger=web_logger, loop=None,
             router = web_urldispatcher.UrlDispatcher()
         assert isinstance(router, AbstractRouter), router
 
-        router.post_init(self)
+        router.add_subapp = _wrap_add_subbapp(self)
 
         if debug is ...:
             debug = loop.get_debug()
@@ -125,6 +126,23 @@ def handler(app):
         reg_handler('on_shutdown')
         reg_handler('on_cleanup')
 
+    def add_subapp(self, prefix, subapp):
+        if self.frozen:
+            raise RuntimeError(
+                "Cannot add sub application to frozen application")
+        if subapp.frozen:
+            raise RuntimeError("Cannot add frozen application")
+        if prefix.endswith('/'):
+            prefix = prefix[:-1]
+        if prefix in ('', '/'):
+            raise ValueError("Prefix cannot be empty")
+
+        resource = PrefixedSubAppResource(prefix, subapp)
+        self.reg_resource(resource)
+        subapp._reg_subapp_signals(subapp)
+        subapp.freeze()
+        return resource
+
     @property
     def on_response_prepare(self):
         return self._on_response_prepare
diff --git a/aiohttp/web_urldispatcher.py b/aiohttp/web_urldispatcher.py
index 017452d0b6f..b0e443475c5 100644
--- a/aiohttp/web_urldispatcher.py
+++ b/aiohttp/web_urldispatcher.py
@@ -714,11 +714,6 @@ def __init__(self):
         super().__init__()
         self._resources = []
         self._named_resources = {}
-        self._app = None
-
-    def post_init(self, app):
-        assert app is not None
-        self._app = app
 
     @asyncio.coroutine
     def resolve(self, request):
@@ -759,16 +754,13 @@ def routes(self):
     def named_resources(self):
         return MappingProxyType(self._named_resources)
 
-    def _reg_resource(self, resource):
+    def reg_resource(self, resource):
         assert isinstance(resource, AbstractResource), \
             'Instance of AbstractResource class is required, got {!r}'.format(
                 resource)
-        if self._app is None:
-            raise RuntimeError(".post_init() should be called before "
-                               "first resource registering")
         if self.frozen:
-            raise RuntimeError("Cannot register a resource into "
-                               "frozen router.")
+            raise RuntimeError(
+                "Cannot register a resource into frozen router.")
 
         name = resource.name
 
@@ -792,7 +784,7 @@ def add_resource(self, path, *, name=None):
             raise ValueError("path should be started with / or be empty")
         if not ('{' in path or '}' in path or self.ROUTE_RE.search(path)):
             resource = PlainResource(quote(path, safe='/'), name=name)
-            self._reg_resource(resource)
+            self.reg_resource(resource)
             return resource
 
         pattern = ''
@@ -823,7 +815,7 @@ def add_resource(self, path, *, name=None):
             raise ValueError(
                 "Bad pattern '{}': {}".format(pattern, exc)) from None
         resource = DynamicResource(compiled, formatter, name=name)
-        self._reg_resource(resource)
+        self.reg_resource(resource)
         return resource
 
     def add_route(self, method, path, handler,
@@ -852,7 +844,7 @@ def add_static(self, prefix, path, *, name=None, expect_handler=None,
                                   response_factory=response_factory,
                                   show_index=show_index,
                                   follow_symlinks=follow_symlinks)
-        self._reg_resource(resource)
+        self.reg_resource(resource)
         return resource
 
     def add_head(self, *args, **kwargs):
@@ -891,20 +883,25 @@ def add_delete(self, *args, **kwargs):
         """
         return self.add_route(hdrs.METH_DELETE, *args, **kwargs)
 
-    def add_subapp(self, prefix, subapp):
+    def freeze(self):
+        super().freeze()
+        for resource in self._resources:
+            resource.freeze()
+
+
+def _wrap_add_subbapp(app):
+
+    def add_subapp(prefix, subapp):
         if subapp.frozen:
-            raise RuntimeError("Cannod add frozen application")
+            raise RuntimeError("Cannot add frozen application")
         if prefix.endswith('/'):
             prefix = prefix[:-1]
         if prefix in ('', '/'):
             raise ValueError("Prefix cannot be empty")
         resource = PrefixedSubAppResource(prefix, subapp)
-        self._reg_resource(resource)
-        self._app._reg_subapp_signals(subapp)
+        app.router.reg_resource(resource)
+        app._reg_subapp_signals(subapp)
         subapp.freeze()
         return resource
 
-    def freeze(self):
-        super().freeze()
-        for resource in self._resources:
-            resource.freeze()
+    return add_subapp
diff --git a/tests/test_urldispatch.py b/tests/test_urldispatch.py
index 996a8c29582..a3819d09232 100644
--- a/tests/test_urldispatch.py
+++ b/tests/test_urldispatch.py
@@ -13,7 +13,7 @@
 from aiohttp.test_utils import make_mocked_request
 from aiohttp.web import HTTPMethodNotAllowed, HTTPNotFound, Response
 from aiohttp.web_urldispatcher import (AbstractResource, ResourceRoute,
-                                       SystemRoute, UrlDispatcher, View,
+                                       SystemRoute, View,
                                        _defaultExpectHandler)
 
 
@@ -1011,9 +1011,3 @@ def test_convert_empty_path_to_slash_on_freezing(router):
     assert resource.get_info() == {'path': ''}
     router.freeze()
     assert resource.get_info() == {'path': '/'}
-
-
-def test_add_to_non_initialized_router():
-    router = UrlDispatcher()
-    with pytest.raises(RuntimeError):
-        router.add_get('/', make_handler())