diff --git a/lua/cmp/utils/window.lua b/lua/cmp/utils/window.lua
index fd0afee..6f87ce4 100644
--- a/lua/cmp/utils/window.lua
+++ b/lua/cmp/utils/window.lua
@@ -25,21 +25,28 @@ local window = {}
 ---@return cmp.Window
 window.new = function()
   local self = setmetatable({}, { __index = window })
-  self.buf = vim.api.nvim_create_buf(false, true)
-  vim.api.nvim_buf_set_option(self.buf, 'undolevels', -1)
-  vim.api.nvim_buf_set_option(self.buf, 'buftype', 'nofile')
+  self:ensure()
   self.win = nil
-  self.style = {}
-  self.sbuf1 = vim.api.nvim_create_buf(false, true)
   self.swin1 = nil
-  self.sbuf2 = vim.api.nvim_create_buf(false, true)
   self.swin2 = nil
+  self.style = {}
   self.cache = cache.new()
   self.opt = {}
   self.id = 0
   return self
 end
 
+---Ensure valid state.
+window.ensure = function(self)
+  for _, name in ipairs({ 'buf', 'sbuf1', 'subf2' }) do
+    if not (self[name] and vim.api.nvim_buf_is_valid(self[name])) then
+      self[name] = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_buf_set_option(self[name], 'undolevels', -1)
+      vim.api.nvim_buf_set_option(self[name], 'buftype', 'nofile')
+    end
+  end
+end
+
 ---Set window option.
 ---NOTE: If the window already visible, immediately applied to it.
 ---@param key string
diff --git a/lua/cmp/view/custom_entries_view.lua b/lua/cmp/view/custom_entries_view.lua
index 7f42c54..b371b35 100644
--- a/lua/cmp/view/custom_entries_view.lua
+++ b/lua/cmp/view/custom_entries_view.lua
@@ -89,6 +89,8 @@ custom_entries_view.redraw = function()
 end
 
 custom_entries_view.open = function(self, offset, entries)
+  self.entries_win:ensure()
+
   self.offset = offset
   self.entries = {}
   self.column_bytes = { abbr = 0, kind = 0, menu = 0 }
diff --git a/lua/cmp/view/docs_view.lua b/lua/cmp/view/docs_view.lua
index aac0cf0..e005903 100644
--- a/lua/cmp/view/docs_view.lua
+++ b/lua/cmp/view/docs_view.lua
@@ -22,6 +22,8 @@ end
 ---@param e cmp.Entry
 ---@param view cmp.WindowStyle
 docs_view.open = function(self, e, view)
+  self.window:ensure()
+
   local documentation = config.get().documentation
   if not documentation then
     return