diff --git a/runtime/autoload/dist/ft.vim b/runtime/autoload/dist/ft.vim
index 5db68d3..48eaf3f 100644
--- a/runtime/autoload/dist/ft.vim
+++ b/runtime/autoload/dist/ft.vim
@@ -878,6 +878,23 @@
   endif
 enddef
 
+# This function checks the first 100 lines of files matching "*.sil" to
+# resolve detection between Swift Intermediate Language and SILE.
+export def FTsil()
+  for lnum in range(1, [line('$'), 100]->min())
+    var line: string = getline(lnum)
+    if line =~ '^\s*[\\%]'
+      setf sile
+      return
+    elseif line =~ '^\s*\S'
+      setf sil
+      return
+    endif
+  endfor
+  # no clue, default to "sil"
+  setf sil
+enddef
+
 export def FTsys()
   if exists("g:filetype_sys")
     exe "setf " .. g:filetype_sys
diff --git a/runtime/filetype.vim b/runtime/filetype.vim
index c2b89a5..c7670d0 100644
--- a/runtime/filetype.vim
+++ b/runtime/filetype.vim
@@ -1822,7 +1822,7 @@
 au BufNewFile,BufRead *.st			setf st
 
 " Smalltalk (and Rexx, TeX, and Visual Basic)
-au BufNewFile,BufRead *.cls                     call dist#ft#FTcls()
+au BufNewFile,BufRead *.cls			call dist#ft#FTcls()
 
 " Smarty templates
 au BufNewFile,BufRead *.tpl			setf smarty
@@ -1929,8 +1929,8 @@
 au BufNewFile,BufRead *.swift			setf swift
 au BufNewFile,BufRead *.swift.gyb		setf swiftgyb
 
-" Swift Intermediate Language
-au BufNewFile,BufRead *.sil			setf sil
+" Swift Intermediate Language or SILE
+au BufNewFile,BufRead *.sil			call dist#ft#FTsil()
 
 " Sysctl
 au BufNewFile,BufRead */etc/sysctl.conf,*/etc/sysctl.d/*.conf	setf sysctl
diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index 18233e7..fbb8d2d 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -1827,6 +1827,44 @@
   filetype off
 endfunc
 
+" Test dist#ft#FTsil()
+func Test_sil_file()
+  filetype on
+
+  split Xfile.sil
+  call assert_equal('sil', &filetype)
+  bwipe!
+
+  let lines =<< trim END
+  // valid
+  let protoErasedPathA = \ABCProtocol.a
+
+  // also valid
+  let protoErasedPathA =
+          \ABCProtocol.a
+  END
+  call writefile(lines, 'Xfile.sil')
+
+  split Xfile.sil
+  call assert_equal('sil', &filetype)
+  bwipe!
+
+  " SILE
+
+  call writefile(['% some comment'], 'Xfile.sil')
+  split Xfile.sil
+  call assert_equal('sile', &filetype)
+  bwipe!
+
+  call writefile(['\begin[papersize=a6]{document}foo\end{document}'], 'Xfile.sil')
+  split Xfile.sil
+  call assert_equal('sile', &filetype)
+  bwipe!
+
+  call delete('Xfile.sil')
+  filetype off
+endfunc
+
 func Test_inc_file()
   filetype on
 
diff --git a/src/version.c b/src/version.c
index 18278c3..f885aa1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -708,6 +708,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    349,
+/**/
     348,
 /**/
     347,