diff --git a/autoload/youcompleteme.vim b/autoload/youcompleteme.vim
index 46cc12a2..ae75ee26 100644
--- a/autoload/youcompleteme.vim
+++ b/autoload/youcompleteme.vim
@@ -206,6 +206,19 @@ function! s:SetUpCompleteopt()
   endif
 endfunction
 
+
+" For various functions/use-cases, we want to keep track of whether the buffer
+" has changed since the last time they were invoked. We keep the state of
+" b:changedtick of the last time the specific function was called in
+" b:ycm_changedtick.
+function! s:SetUpYcmChangedTick()
+  let b:ycm_changedtick  =
+        \ get( b:, 'ycm_changedtick', {
+        \   'file_ready_to_parse' : -1,
+        \ } )
+endfunction
+
+
 function! s:OnVimLeave()
   py ycm_state.OnVimLeave()
   py extra_conf_store.CallExtraConfVimCloseIfExists()
@@ -213,6 +226,11 @@ endfunction
 
 
 function! s:OnBufferVisit()
+  " We need to do this even when we are not allowed to complete in the current
+  " file because we might be allowed to complete in the future! The canonical
+  " example is creating a new buffer with :enew and then setting a filetype.
+  call s:SetUpYcmChangedTick()
+
   if !s:AllowedToCompleteInCurrentFile()
     return
   endif
@@ -247,7 +265,11 @@ endfunction
 
 
 function! s:OnFileReadyToParse()
-  py ycm_state.OnFileReadyToParse()
+  let buffer_changed = b:changedtick != b:ycm_changedtick.file_ready_to_parse
+  if buffer_changed
+    py ycm_state.OnFileReadyToParse()
+  endif
+  let b:ycm_changedtick.file_ready_to_parse = b:changedtick
 endfunction