diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 4053e51..25c7f57 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -3,7 +3,7 @@
 # Vim functions for file type detection
 #
 # Maintainer:		The Vim Project <https://github.com/vim/vim>
-# Last Change:		2025 Apr 10
+# Last Change:		2025 Apr 15
 # Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 # These functions are moved here from runtime/filetype.vim to make startup
@@ -595,11 +595,15 @@
 # This function checks if one of the first five lines start with a dot.  In
 # that case it is probably an nroff file: 'filetype' is set and 1 is returned.
 export def FTnroff(): number
-  if getline(1)[0] .. getline(2)[0] .. getline(3)[0]
-    			.. getline(4)[0] .. getline(5)[0] =~ '\.'
-    setf nroff
-    return 1
-  endif
+  var n = 1
+  while n < 5
+    var line = getline(n)
+    if line =~ '^\.\S\S\?'
+      setf nroff
+      return 1
+    endif
+    n += 1
+  endwhile
   return 0
 enddef