diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 5014e75442..ff1dc037d2 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -3,7 +3,7 @@ vim9script
 # Vim functions for file type detection
 #
 # Maintainer:		The Vim Project <https://github.com/vim/vim>
-# Last Change:		2025 Jun 17
+# Last Change:		2025 Jul 08
 # Former Maintainer:	Bram Moolenaar <Bram@vim.org>
 
 # These functions are moved here from runtime/filetype.vim to make startup
@@ -30,12 +30,8 @@ export def Check_inp()
 enddef
 
 # This function checks for the kind of assembly that is wanted by the user, or
-# can be detected from the first five lines of the file.
+# can be detected from the beginning of the file.
 export def FTasm()
-  # tiasm uses `* commment`
-  if join(getline(1, 10), "\n") =~ '\%(\%(^\|\n\)\*\|Texas Instruments Incorporated\)'
-    setf tiasm
-  endif
   # make sure b:asmsyntax exists
   if !exists("b:asmsyntax")
     b:asmsyntax = ""
@@ -65,8 +61,26 @@ export def FTasmsyntax()
   var match = matchstr(head, '\sasmsyntax=\zs[a-zA-Z0-9]\+\ze\s')
   if match != ''
     b:asmsyntax = match
-  elseif ((head =~? '\.title') || (head =~? '\.ident') || (head =~? '\.macro') || (head =~? '\.subtitle') || (head =~? '\.library'))
-    b:asmsyntax = "vmasm"
+  else
+    # Use heuristics
+    var is_slash_star_encountered = false
+    var i = 1
+    const n = min([50, line("$")])
+    while i <= n
+      const line = getline(i)
+      if line =~ '\%(^\|\n\)/\*'
+        is_slash_star_encountered = true
+      endif
+      if line =~# '^; Listing generated by Microsoft' || line =~? '\%(^\|\n\)\%(\%(CONST\|_BSS\|_DATA\|_TEXT\)\s\+SEGMENT\>\)\|\s*\.[2-6]86P\?\>\|\s*\.XMM\>'
+        b:asmsyntax = "masm"
+      elseif line =~ 'Texas Instruments Incorporated' || (line =~ '\%(^\|\n\)\*' && !is_slash_star_encountered)
+        # tiasm uses `* commment`, but detection is unreliable if '/*' is seen
+        b:asmsyntax = "tiasm"
+      elseif ((line =~? '\.title\>\|\.ident\>\|\.macro\>\|\.subtitle\>\|\.library\>'))
+        b:asmsyntax = "vmasm"
+      endif
+      i += 1
+    endwhile
   endif
 enddef