diff --git a/autoload/vimtex/state/class.vim b/autoload/vimtex/state/class.vim
index d3bf107a04..8a8cae727e 100644
--- a/autoload/vimtex/state/class.vim
+++ b/autoload/vimtex/state/class.vim
@@ -18,8 +18,7 @@ function! vimtex#state#class#new(main, main_parser, preserve_root) abort " {{{1
   endif
 
   let l:ext = fnamemodify(a:main, ':e')
-  let l:new.tex = index(['tex', 'dtx', 'tikz', 'ins'], l:ext) >= 0
-        \ ? a:main : ''
+  let l:new.tex = l:ext =~? '\v^%(%(la)?tex|dtx|tikz|ins)$' ? a:main : ''
 
   " Get preamble for some state parsing
   let l:preamble = !empty(l:new.tex)