diff --git a/src/testdir/test_filetype.vim b/src/testdir/test_filetype.vim
index ebf6eb0..3b875bb 100644
--- a/src/testdir/test_filetype.vim
+++ b/src/testdir/test_filetype.vim
@@ -182,11 +182,12 @@
     \ 'fgl': ['file.4gl', 'file.4gh', 'file.m4gl'],
     \ 'fish': ['file.fish'],
     \ 'focexec': ['file.fex', 'file.focexec'],
-    \ 'forth': ['file.fs', 'file.ft', 'file.fth'],
+    \ 'forth': ['file.ft', 'file.fth'],
     \ 'fortran': ['file.f', 'file.for', 'file.fortran', 'file.fpp', 'file.ftn', 'file.f77', 'file.f90', 'file.f95', 'file.f03', 'file.f08'],
     \ 'fpcmake': ['file.fpc'],
     \ 'framescript': ['file.fsl'],
     \ 'freebasic': ['file.fb', 'file.bi'],
+    \ 'fs': ['file.fs'],
     \ 'fstab': ['fstab', 'mtab'],
     \ 'fvwm': ['/.fvwm/file', 'any/.fvwm/file'],
     \ 'gdb': ['.gdbinit', 'gdbinit'],
@@ -664,6 +665,7 @@
       \ 'fennel': [['#!/path/fennel']],
       \ 'routeros': [['#!/path/rsc']],
       \ 'fish': [['#!/path/fish']],
+      \ 'forth': [['#!/path/gforth']],
       \ }
 
 " Various forms of "env" optional arguments.
@@ -970,4 +972,57 @@
   filetype off
 endfunc
 
+func Test_fs_file()
+  filetype on
+
+  call writefile(['looks like F#'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('fs', &filetype)
+  bwipe!
+
+  let g:filetype_fs = 'forth'
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+  unlet g:filetype_fs
+
+  " Test dist#ft#FTfs()
+
+  " Forth (Gforth)
+
+  call writefile(['( Forth inline comment )'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile(['.( Forth displayed inline comment )'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile(['\ Forth line comment'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  " empty line comment - no space required
+  call writefile(['\'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile(['\G Forth documentation comment '], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call writefile([': squared ( n -- n^2 )', 'dup * ;'], 'Xfile.fs')
+  split Xfile.fs
+  call assert_equal('forth', &filetype)
+  bwipe!
+
+  call delete('Xfile.fs')
+  filetype off
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/version.c b/src/version.c
index 5483fe6..9456737 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3686,
+/**/
     3685,
 /**/
     3684,