diff --git a/lua/vimtex/bibparser.lua b/lua/vimtex/bibparser.lua
index ffb552e354..abf05b72b8 100644
--- a/lua/vimtex/bibparser.lua
+++ b/lua/vimtex/bibparser.lua
@@ -10,12 +10,12 @@
 ---@return table current Current entry with updated body
 local function parse_tail(current, line)
   current.level = current.level
-    + vim.fn.count(line, "{")
-    - vim.fn.count(line, "}")
+    + line:gsub("[^{]", ""):len()
+    - line:gsub("[^}]", ""):len()
   if current.level > 0 then
     current.body = current.body .. line
   else
-    current.body = current.body .. vim.fn.matchstr(line, [[.*\ze}]])
+    current.body = current.body .. line:match(".*}()")
     current.parsed = true
   end
 
@@ -29,7 +29,7 @@ end
 ---@return table current Current entry with updated body
 local function parse_head(file, lnum, line)
   local matches = vim.fn.matchlist(line, [[\v^\@(\w+)\s*\{\s*(.*)]])
-  if vim.tbl_isempty(matches) then
+  if #matches == 0 then
     return {}
   end
 
@@ -93,7 +93,8 @@ local function get_tag_value(body, head, strings)
   -- First check if the value is simply a number
   if vim.regex([[\d]]):match_str(body:sub(head + 1, head + 1)) then
     local value = vim.fn.matchstr(body, [[^\d\+]], head)
-    local new_head = vim.fn.matchend(body, [[^\s*,\s*]], head + vim.fn.len(value))
+    local new_head =
+      vim.fn.matchend(body, [[^\s*,\s*]], head + vim.fn.len(value))
     return value, new_head
   end
 
@@ -131,7 +132,7 @@ end
 ---@return integer head New head position
 local function get_tag_name(body, head)
   local matches = vim.fn.matchlist(body, [[^\v([-_:0-9a-zA-Z]+)\s*\=\s*]], head)
-  if vim.tbl_isempty(matches) then
+  if #matches == 0 then
     return "", -1
   end
 
@@ -146,21 +147,22 @@ local function parse_item(item, strings)
   local parts = vim.fn.matchlist(item.body, [[\v^([^, ]*)\s*,\s*(.*)]])
 
   item.level = nil
+  item.parsed = nil
   item.body = nil
   item.key = parts[2]
   local body = parts[3]
 
-  if vim.fn.empty(body) == 1 then
+  if body == nil or body == "" then
     return nil
   end
 
   local tag = ""
+  local value
   local head = 0
   while head >= 0 do
-    if vim.fn.empty(tag) == 1 then
+    if tag == "" then
       tag, head = get_tag_name(body, head)
     else
-      local value
       value, head = get_tag_value(body, head, strings)
       item[tag] = value
       tag = ""
@@ -175,7 +177,8 @@ end
 ---@return string? key
 ---@return string? value
 local function parse_string(raw_string)
-  local matches = vim.fn.matchlist(raw_string, [[\v^\s*(\S+)\s*\=\s*"(.*)"\s*$]])
+  local matches =
+    vim.fn.matchlist(raw_string, [[\v^\s*(\S+)\s*\=\s*"(.*)"\s*$]])
   if vim.fn.empty(matches[3]) == 0 then
     return matches[2], matches[3]
   end