diff --git a/runtime/lua/vim/filetype.lua b/runtime/lua/vim/filetype.lua
index a287607386..bfe700f8dd 100644
--- a/runtime/lua/vim/filetype.lua
+++ b/runtime/lua/vim/filetype.lua
@@ -280,12 +280,7 @@ local extension = {
   cfi = 'cf',
   hgrc = 'cfg',
   cfg = detect.cfg,
-  cfG = detect.cfg,
-  cFg = detect.cfg,
-  cFG = detect.cfg,
   Cfg = detect.cfg,
-  CfG = detect.cfg,
-  CFg = detect.cfg,
   CFG = detect.cfg,
   chf = 'ch',
   chai = 'chaiscript',
@@ -370,12 +365,7 @@ local extension = {
   drt = 'dart',
   ds = 'datascript',
   dat = detect.dat,
-  daT = detect.dat,
-  dAt = detect.dat,
-  dAT = detect.dat,
   Dat = detect.dat,
-  DaT = detect.dat,
-  DAt = detect.dat,
   DAT = detect.dat,
   dcd = 'dcd',
   decl = detect.decl,
@@ -658,12 +648,7 @@ local extension = {
   kt = 'kotlin',
   ktm = 'kotlin',
   sub = 'krl',
-  suB = 'krl',
-  sUb = 'krl',
-  sUB = 'krl',
   Sub = 'krl',
-  SuB = 'krl',
-  SUb = 'krl',
   SUB = 'krl',
   ks = 'kscript',
   k = 'kwt',
@@ -699,12 +684,7 @@ local extension = {
   lite = 'lite',
   livemd = 'livebook',
   log = detect.log,
-  loG = detect.log,
-  lOg = detect.log,
-  lOG = detect.log,
   Log = detect.log,
-  LoG = detect.log,
-  LOg = detect.log,
   LOG = detect.log,
   lgt = 'logtalk',
   lotos = 'lotos',
@@ -773,12 +753,7 @@ local extension = {
   mmp = 'mmp',
   mms = detect.mms,
   mod = detect.mod,
-  moD = detect.mod,
-  mOd = detect.mod,
-  mOD = detect.mod,
   Mod = detect.mod,
-  MoD = detect.mod,
-  MOd = detect.mod,
   MOD = detect.mod,
   DEF = 'modula2',
   m3 = 'modula3',
@@ -948,12 +923,7 @@ local extension = {
   ih = 'ppwiz',
   action = 'privoxy',
   prg = detect.prg,
-  prG = detect.prg,
-  pRg = detect.prg,
-  pRG = detect.prg,
   Prg = detect.prg,
-  PrG = detect.prg,
-  PRg = detect.prg,
   PRG = detect.prg,
   pc = 'proc',
   pdb = 'prolog',
@@ -1133,12 +1103,7 @@ local extension = {
   sqr = 'sqr',
   nut = 'squirrel',
   src = detect.src,
-  srC = detect.src,
-  sRc = detect.src,
-  sRC = detect.src,
   Src = detect.src,
-  SrC = detect.src,
-  SRc = detect.src,
   SRC = detect.src,
   s28 = 'srec',
   s37 = 'srec',
@@ -1168,12 +1133,7 @@ local extension = {
   swig = 'swig',
   swg = 'swig',
   sys = detect.sys,
-  syS = detect.sys,
-  sYs = detect.sys,
-  sYS = detect.sys,
   Sys = detect.sys,
-  SyS = detect.sys,
-  SYs = detect.sys,
   SYS = detect.sys,
   svh = 'systemverilog',
   sv = 'systemverilog',
diff --git a/test/old/testdir/test_filetype.vim b/test/old/testdir/test_filetype.vim
index 9c47dfa16f..33f8df4081 100644
--- a/test/old/testdir/test_filetype.vim
+++ b/test/old/testdir/test_filetype.vim
@@ -1150,15 +1150,14 @@ func Test_cfg_file()
   unlet g:filetype_cfg
 
   " RAPID cfg
-  let ext = 'cfg'
   for i in ['EIO', 'MMC', 'MOC', 'PROC', 'SIO', 'SYS']
-    call writefile([i .. ':CFG'], 'cfgfile.' .. ext)
-    execute "split cfgfile." .. ext
-    call assert_equal('rapid', &filetype)
-    bwipe!
-    call delete('cfgfile.' .. ext)
-    " check different case of file extension
-    let ext = substitute(ext, '\(\l\)', '\u\1', '')
+    for ext in ['cfg', 'Cfg', 'CFG']
+      call writefile([i .. ':CFG'], 'cfgfile.' .. ext)
+      execute "split cfgfile." .. ext
+      call assert_equal('rapid', &filetype)
+      bwipe!
+      call delete('cfgfile.' .. ext)
+    endfor
   endfor
 
   " clean up