diff --git a/lua/outline/config.lua b/lua/outline/config.lua
index 606cd38..bb3b037 100644
--- a/lua/outline/config.lua
+++ b/lua/outline/config.lua
@@ -208,7 +208,7 @@ end
 ---@param bufnr integer
 ---@return boolean include
 function M.should_include_symbol(kind, bufnr)
-  local ft = vim.api.nvim_buf_get_option(bufnr, 'ft')
+  local ft = vim.api.nvim_get_option_value('ft', { buf = bufnr })
   -- There can only be one kind in markdown and norg as of now
   if ft == 'markdown' or ft == 'norg' or kind == nil then
     return true
@@ -232,7 +232,7 @@ function M.should_include_symbol(kind, bufnr)
   return filter_table[kind] ~= false
 end
 
----@param client lsp.client|number
+---@param client vim.lsp.Client|number
 function M.is_client_blacklisted(client)
   if not client then
     return false
diff --git a/lua/outline/float.lua b/lua/outline/float.lua
index bd283fe..839e013 100644
--- a/lua/outline/float.lua
+++ b/lua/outline/float.lua
@@ -68,7 +68,19 @@ function Float:open(lines, hl, title, indent)
   if hl then
     self.ns = vim.api.nvim_create_namespace('OutlineHelp')
     for _, h in ipairs(hl) do
-      vim.hl.range(self.bufnr, self.ns, h.name, { h.line, h.from + indent }, { h.line, (h.to ~= -1 and h.to + indent) or -1 })
+      if _G._outline_nvim_has[11] then
+        vim.hl.range(self.bufnr, self.ns, h.name, { h.line, h.from + indent }, { h.line, (h.to ~= -1 and h.to + indent) or -1 })
+      else
+        ---@diagnostic disable-next-line:deprecated
+        vim.api.nvim_buf_add_highlight(
+          self.bufnr,
+          self.ns,
+          h.name,
+          h.line,
+          h.from + indent,
+          (h.to ~= -1 and h.to + indent) or -1
+        )
+      end
     end
   end
 end
diff --git a/lua/outline/highlight.lua b/lua/outline/highlight.lua
index 0e33fd6..4f80cc3 100644
--- a/lua/outline/highlight.lua
+++ b/lua/outline/highlight.lua
@@ -29,7 +29,14 @@ function M.hovers(bufnr, nodes)
   for line, node in ipairs(nodes) do
     if node.hovered then
       -- stylua: ignore start
-      vim.hl.range(bufnr, M.ns.hover, 'OutlineCurrent', { line - 1, node.prefix_length }, { line - 1, -1 })
+      if _G._outline_nvim_has[11] then
+        vim.hl.range(bufnr, M.ns.hover, 'OutlineCurrent', { line - 1, node.prefix_length }, { line - 1, -1 })
+      else
+        ---@diagnostic disable-next-line:deprecated
+        vim.api.nvim_buf_add_highlight(
+          bufnr, M.ns.hover, 'OutlineCurrent', line - 1, node.prefix_length, -1
+        )
+      end
       -- stylua: ignore end
     end
   end
@@ -41,7 +48,14 @@ end
 function M.items(bufnr, hl_list)
   for _, h in ipairs(hl_list) do
     -- stylua: ignore start
-    vim.hl.range(bufnr, M.ns.items, h.name, { h.line - 1, h.from }, { h.line - 1, h.to })
+    if _G._outline_nvim_has[11] then
+      vim.hl.range(bufnr, M.ns.items, h.name, { h.line - 1, h.from }, { h.line - 1, h.to })
+    else
+      ---@diagnostic disable-next-line:deprecated
+      vim.api.nvim_buf_add_highlight(
+        bufnr, M.ns.items, h.name, h.line - 1, h.from, h.to
+      )
+    end
     -- stylua: ignore end
   end
 end
diff --git a/lua/outline/init.lua b/lua/outline/init.lua
index 9859f6c..0d3ab90 100644
--- a/lua/outline/init.lua
+++ b/lua/outline/init.lua
@@ -351,6 +351,7 @@ function M.setup(opts)
     [8] = minor >= 8,
     [9] = minor >= 9,
     [10] = minor >= 10,
+    [11] = minor >= 11,
   }
 
   cfg.setup(opts)
diff --git a/lua/outline/providers/nvim-lsp.lua b/lua/outline/providers/nvim-lsp.lua
index ba41683..dcb45be 100644
--- a/lua/outline/providers/nvim-lsp.lua
+++ b/lua/outline/providers/nvim-lsp.lua
@@ -18,7 +18,7 @@ function M.get_status(info)
   return { 'client: ' .. info.client.name }
 end
 
----@param client lsp.client
+---@param client vim.lsp.Client
 ---@param capability string
 ---@return boolean
 local function _check_client(client, capability)
@@ -30,7 +30,7 @@ end
 
 ---@param bufnr integer
 ---@param capability string
----@return lsp.client?
+---@return vim.lsp.Client?
 local function get_appropriate_client(bufnr, capability)
   local clients, use_client
 
@@ -98,14 +98,22 @@ function M.request_symbols(on_symbols, opts, info)
     textDocument = l.util.make_text_document_params(),
   }
   -- XXX: Is bufnr=0 ok here?
-  local status = info.client:request('textDocument/documentSymbol', params, function(err, response)
+  local method = 'textDocument/documentSymbol'
+  local callback = function(err, response)
     if err or not response then
       on_symbols(response, opts)
     else
       response = postprocess_symbols(response)
       on_symbols(response, opts)
     end
-  end, 0)
+  end
+  local bufnr = 0
+  local status
+  if _G._outline_nvim_has[11] then
+    status = info.client:request(method, params, callback, bufnr)
+  else
+    status = info.client.request(method, params, callback, bufnr)
+  end
   if not status then
     on_symbols(nil, opts)
   end
@@ -135,7 +143,7 @@ end
 
 ---@see rename_symbol
 ---@param sidebar outline.Sidebar
----@param client lsp.client
+---@param client vim.lsp.Client
 ---@param node outline.FlatSymbol
 ---@return boolean success
 local function legacy_rename(sidebar, client, node)
@@ -151,8 +159,13 @@ local function legacy_rename(sidebar, client, node)
     bufnr = sidebar.code.buf,
     newName = new_name,
   }
-  local status, err =
-    client:request_sync('textDocument/rename', params, request_timeout, sidebar.code.buf)
+  local status, err
+  if _G._outline_nvim_has[11] then
+    status, err = client:request_sync('textDocument/rename', params, request_timeout, sidebar.code.buf)
+  else
+    ---@diagnostic disable-next-line
+    status, err = client.request_sync('textDocument/rename', params, request_timeout, sidebar.code.buf)
+  end
   if status == nil or status.err or err or status.result == nil then
     return false
   end
@@ -211,7 +224,12 @@ function M.show_hover(sidebar)
     bufnr = sidebar.code.buf,
   }
 
-  local status, err = client:request_sync('textDocument/hover', params, request_timeout)
+  local status, err
+  if _G._outline_nvim_has[11] then
+    status, err = client:request_sync('textDocument/hover', params, request_timeout)
+  else
+    status, err = client.request_sync('textDocument/hover', params, request_timeout)
+  end
   if status == nil or status.err or err or not status.result or not status.result.contents then
     return false
   end
diff --git a/lua/outline/utils/init.lua b/lua/outline/utils/init.lua
index 05ce12f..4541185 100644
--- a/lua/outline/utils/init.lua
+++ b/lua/outline/utils/init.lua
@@ -38,7 +38,14 @@ function M.flash_highlight(winnr, lnum, durationMs, hl_group)
     durationMs = 400
   end
   local bufnr = vim.api.nvim_win_get_buf(winnr)
-  local ns = vim.api.nvim_buf_add_highlight(bufnr, 0, hl_group, lnum - 1, 0, -1)
+  local ns
+  if _G._outline_nvim_has[11] then
+    ns = vim.api.nvim_create_namespace("_outline_nvim_flash")
+    vim.hl.range(bufnr, ns, hl_group, { lnum-1, 0 }, { lnum-1, -1 })
+  else
+    ---@diagnostic disable-next-line:deprecated
+    ns = vim.api.nvim_buf_add_highlight(bufnr, 0, hl_group, lnum - 1, 0, -1)
+  end
   local remove_highlight = function()
     pcall(vim.api.nvim_buf_clear_namespace, bufnr, ns, 0, -1)
   end