diff --git a/runtime/lua/vim/filetype.lua b/runtime/lua/vim/filetype.lua
index 8e1ee50c01..80a9a1bdc9 100644
--- a/runtime/lua/vim/filetype.lua
+++ b/runtime/lua/vim/filetype.lua
@@ -464,6 +464,7 @@ local extension = {
   ['4gh'] = 'fgl',
   fir = 'firrtl',
   fish = 'fish',
+  flix = 'flix',
   focexec = 'focexec',
   fex = 'focexec',
   ft = 'forth',
diff --git a/test/old/testdir/test_filetype.vim b/test/old/testdir/test_filetype.vim
index 3d66fd5538..e1775af16b 100644
--- a/test/old/testdir/test_filetype.vim
+++ b/test/old/testdir/test_filetype.vim
@@ -287,6 +287,7 @@ func s:GetFilenameChecks() abort
     \ 'fgl': ['file.4gl', 'file.4gh', 'file.m4gl'],
     \ 'firrtl': ['file.fir'],
     \ 'fish': ['file.fish'],
+    \ 'flix': ['file.flix'],
     \ 'focexec': ['file.fex', 'file.focexec'],
     \ 'form': ['file.frm'],
     \ 'forth': ['file.ft', 'file.fth', 'file.4th'],