diff --git a/autoload/youcompleteme.vim b/autoload/youcompleteme.vim
index 38515418..1f8a6a15 100644
--- a/autoload/youcompleteme.vim
+++ b/autoload/youcompleteme.vim
@@ -423,7 +423,10 @@ endfunction
 function! s:SetCompleteFunc()
   let &completefunc = 'youcompleteme#Complete'
   let &l:completefunc = 'youcompleteme#Complete'
+endfunction
 
+
+function! s:SetOmnicompleteFunc()
   if pyeval( 'ycm_state.NativeFiletypeCompletionUsable()' )
     let &omnifunc = 'youcompleteme#OmniComplete'
     let &l:omnifunc = 'youcompleteme#OmniComplete'
@@ -505,6 +508,11 @@ function! s:OnInsertEnter()
     return
   endif
 
+  if get( b:, 'ycm_omnicomplete', 0 )
+    let b:ycm_omnicomplete = 1
+    call s:SetOmnicompleteFunc()
+  endif
+
   let s:old_cursor_position = []
 endfunction
 
@@ -559,8 +567,7 @@ endfunction
 
 function! s:UpdateDiagnosticNotifications()
   let should_display_diagnostics = g:ycm_show_diagnostics_ui &&
-        \ s:DiagnosticUiSupportedForCurrentFiletype() &&
-        \ pyeval( 'ycm_state.NativeFiletypeCompletionUsable()' )
+        \ s:DiagnosticUiSupportedForCurrentFiletype()
 
   if !should_display_diagnostics
     return
diff --git a/python/ycm/client/completer_available_request.py b/python/ycm/client/completer_available_request.py
new file mode 100644
index 00000000..3b12b6b2
--- /dev/null
+++ b/python/ycm/client/completer_available_request.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2013  Google Inc.
+#
+# This file is part of YouCompleteMe.
+#
+# YouCompleteMe is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# YouCompleteMe is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with YouCompleteMe.  If not, see <http://www.gnu.org/licenses/>.
+
+from ycm.client.base_request import ( BaseRequest, BuildRequestData,
+                                      HandleServerException )
+
+class CompleterAvailableRequest( BaseRequest ):
+  def __init__( self, filetypes ):
+    super( CompleterAvailableRequest, self ).__init__()
+    self.filetypes = filetypes
+    self._response = None
+
+
+  def Start( self ):
+    request_data = BuildRequestData()
+    request_data.update( { 'filetypes': self.filetypes } )
+    try:
+      self._response = self.PostDataToHandler( request_data,
+                                               'semantic_completion_available' )
+    except Exception as e:
+      HandleServerException( e )
+
+
+  def Response( self ):
+    return self._response
+
+
+def SendCompleterAvailableRequest( filetypes ):
+  request = CompleterAvailableRequest( filetypes )
+  # This is a blocking call.
+  request.Start()
+  return request.Response()
diff --git a/python/ycm/youcompleteme.py b/python/ycm/youcompleteme.py
index 58cdb2e1..d9147686 100644
--- a/python/ycm/youcompleteme.py
+++ b/python/ycm/youcompleteme.py
@@ -30,9 +30,9 @@ from ycmd.request_wrap import RequestWrap
 from ycm.diagnostic_interface import DiagnosticInterface
 from ycm.omni_completer import OmniCompleter
 from ycm import syntax_parse
-from ycmd.completers.completer_utils import FiletypeCompleterExistsForFiletype
 from ycm.client.ycmd_keepalive import YcmdKeepalive
 from ycm.client.base_request import BaseRequest, BuildRequestData
+from ycm.client.completer_available_request import SendCompleterAvailableRequest
 from ycm.client.command_request import SendCommandRequest
 from ycm.client.completion_request import CompletionRequest
 from ycm.client.omni_completion_request import OmniCompletionRequest
@@ -98,6 +98,7 @@ class YouCompleteMe( object ):
     self._ycmd_keepalive.Start()
 
   def _SetupServer( self ):
+    self._available_completers = {}
     server_port = utils.GetUnusedLocalhostPort()
     # The temp options file is deleted by ycmd during startup
     with tempfile.NamedTemporaryFile( delete = False ) as options_file:
@@ -217,8 +218,20 @@ class YouCompleteMe( object ):
     return self._omnicomp
 
 
+  def FiletypeCompleterExistsForFiletype( self, filetype ):
+    try:
+      return self._available_completers[ filetype ]
+    except KeyError:
+      pass
+
+    exists_completer = ( self.IsServerAlive() and
+                         bool( SendCompleterAvailableRequest( filetype ) ) )
+    self._available_completers[ filetype ] = exists_completer
+    return exists_completer
+
+
   def NativeFiletypeCompletionAvailable( self ):
-    return any( [ FiletypeCompleterExistsForFiletype( x ) for x in
+    return any( [ self.FiletypeCompleterExistsForFiletype( x ) for x in
                   vimsupport.CurrentFiletypes() ] )
 
 
@@ -299,10 +312,10 @@ class YouCompleteMe( object ):
 
 
   def UpdateDiagnosticInterface( self ):
-    if not self.DiagnosticsForCurrentFileReady():
-      return
-    self._diag_interface.UpdateWithNewDiagnostics(
-      self.GetDiagnosticsFromStoredRequest() )
+    if ( self.DiagnosticsForCurrentFileReady() and
+         self.NativeFiletypeCompletionUsable() ):
+      self._diag_interface.UpdateWithNewDiagnostics(
+        self.GetDiagnosticsFromStoredRequest() )
 
 
   def ShowDetailedDiagnostic( self ):