diff --git a/lua/gitlab/actions/discussions/init.lua b/lua/gitlab/actions/discussions/init.lua
index 98cbfde5..51a5c7e5 100644
--- a/lua/gitlab/actions/discussions/init.lua
+++ b/lua/gitlab/actions/discussions/init.lua
@@ -90,6 +90,7 @@ M.initialize_discussions = function()
   end)
   reviewer.set_callback_for_buf_read(function(args)
     vim.api.nvim_set_option_value("modifiable", false, { buf = args.buf })
+    reviewer.update_winid_for_buffer(args.buf)
     reviewer.set_keymaps(args.buf)
     reviewer.set_reviewer_autocommands(args.buf)
   end)
diff --git a/lua/gitlab/reviewer/init.lua b/lua/gitlab/reviewer/init.lua
index 28d85f5c..3b276a38 100644
--- a/lua/gitlab/reviewer/init.lua
+++ b/lua/gitlab/reviewer/init.lua
@@ -59,9 +59,9 @@ M.open = function()
     end
   end
 
+  M.is_open = true
   vim.api.nvim_command(string.format("%s %s..%s", diffview_open_command, diff_refs.base_sha, diff_refs.head_sha))
 
-  M.is_open = true
   M.diffview = require("diffview.lib").get_current_view()
   if M.diffview == nil then
     u.notify("Could not find Diffview view", vim.log.levels.ERROR)
@@ -304,7 +304,11 @@ M.set_callback_for_buf_read = function(callback)
     pattern = { "DiffviewDiffBufRead" },
     group = group,
     callback = function(...)
-      if vim.api.nvim_get_current_tabpage() == M.tabid then
+      -- Only run the callback when we're in the MR's tabpage or when the tabpage has
+      -- not yet been set (tabid = nil) in a freshly started review (is_open = true).
+      -- TODO: This is a hacky workaround for cases when an added file is diffeed
+      -- against diffview://null and this autocommand fires before tabid is set.
+      if vim.api.nvim_get_current_tabpage() == M.tabid or (M.is_open and M.tabid == nil) then
         callback(...)
       end
     end,