diff --git a/lua/telescope/config.lua b/lua/telescope/config.lua
index 2960cdd..80e29c2 100644
--- a/lua/telescope/config.lua
+++ b/lua/telescope/config.lua
@@ -845,6 +845,9 @@ function config.set_defaults(user_defaults, tele_defaults)
       if user_defaults[name] == false or config.values[name] == false then
         return false
       end
+      if user_defaults[name] == true then
+        return vim.F.if_nil(config.values[name], {})
+      end
 
       return smarter_depth_2_extend(
         vim.F.if_nil(user_defaults[name], {}),
diff --git a/lua/telescope/previewers/buffer_previewer.lua b/lua/telescope/previewers/buffer_previewer.lua
index 5117b1f..cd795f1 100644
--- a/lua/telescope/previewers/buffer_previewer.lua
+++ b/lua/telescope/previewers/buffer_previewer.lua
@@ -152,11 +152,13 @@ local scroll_fn = function(self, direction)
 end
 
 previewers.file_maker = function(filepath, bufnr, opts)
-  opts = opts or {}
-  opts.preview = opts.preview or {}
+  opts = vim.F.if_nil(opts, {})
+  -- TODO(conni2461): here shouldn't be any hardcoded magic numbers ...
+  opts.preview = vim.F.if_nil(opts.preview, {})
   opts.preview.timeout = vim.F.if_nil(opts.preview.timeout, 250) -- in ms
   opts.preview.filesize_limit = vim.F.if_nil(opts.preview.filesize_limit, 25) -- in mb
   opts.preview.msg_bg_fillchar = vim.F.if_nil(opts.preview.msg_bg_fillchar, "╱") -- in mb
+  opts.preview.treesitter = vim.F.if_nil(opts.preview.treesitter, true)
   if opts.use_ft_detect == nil then
     opts.use_ft_detect = true
   end
diff --git a/lua/telescope/previewers/utils.lua b/lua/telescope/previewers/utils.lua
index 44a6160..bd8c300 100644
--- a/lua/telescope/previewers/utils.lua
+++ b/lua/telescope/previewers/utils.lua
@@ -78,9 +78,22 @@ end
 
 --- Attach default highlighter which will choose between regex and ts
 utils.highlighter = function(bufnr, ft, opts)
-  opts = opts or {}
-  opts.preview = opts.preview or {}
-  opts.preview.treesitter = vim.F.if_nil(opts.preview.treesitter, conf.preview.treesitter)
+  opts = vim.F.if_nil(opts, {})
+  opts.preview = vim.F.if_nil(opts.preview, {})
+  opts.preview.treesitter = (function()
+    if type(opts.preview) == "table" and opts.preview.treesitter then
+      return opts.preview.treesitter
+    end
+    if type(conf.preview) == "table" and conf.preview.treesitter then
+      return conf.preview.treesitter
+    end
+    if type(conf.preview) == "boolean" then
+      return conf.preview
+    end
+    -- We should never get here
+    return false
+  end)()
+
   if type(opts.preview.treesitter) == "boolean" then
     local temp = { enable = opts.preview.treesitter }
     opts.preview.treesitter = temp