diff --git a/autoload/vimtex/syntax.vim b/autoload/vimtex/syntax.vim
index 68229b879a..b66e699cdd 100644
--- a/autoload/vimtex/syntax.vim
+++ b/autoload/vimtex/syntax.vim
@@ -26,13 +26,29 @@ endfunction
 
 " }}}1
 function! vimtex#syntax#in_mathzone(...) abort " {{{1
-  " The following checks if we are inside a texMathZone environment. The
-  " arguments to \label{...}, the texRefArg group, and \text{...} like
-  " commands, the texMathTextArg group, are actively ignored as these should
-  " not be considered to be math environments.
   let l:groups = reverse(call('vimtex#syntax#stack', a:000))
-  let l:group = matchstr(l:groups, '\v^tex%(Math%(Zone|Text|Tag)|RefArg)')
+  let l:group = matchstr(l:groups, s:__mathzone_regex)
   return l:group =~# '^texMathZone'
 endfunction
 
+" This specifies matchers that are combined for finding the group used to
+" determine if we are in a mathzone. The first entry is `texMathZone`, which
+" indicates that we are in a mathzone. The other entries are groups that
+" indicate specifically that we are NOT in a mathzone. The entries here are
+" part of the core spec. Extensions can register more groups that should be
+" ignored with vimtex#syntax#register_mathzone_ignore.
+let s:__mathzone_matchers = [
+      \ 'texMathZone',
+      \ 'texMathText',
+      \ 'texMathTag',
+      \ 'texRefArg',
+      \]
+let s:__mathzone_regex = '^\%(' . join(s:__mathzone_matchers, '\|') . '\)'
+
+" }}}1
+function! vimtex#syntax#add_to_mathzone_ignore(regex) abort " {{{1
+  let s:__mathzone_matchers += [a:regex]
+  let s:__mathzone_regex = '^\%(' . join(s:__mathzone_matchers, '\|') . '\)'
+endfunction
+
 " }}}1
diff --git a/test/test-syntax/test-custom.tex b/test/test-syntax/test-custom.tex
index 625dc6e48e..dbeb09aa1b 100644
--- a/test/test-syntax/test-custom.tex
+++ b/test/test-syntax/test-custom.tex
@@ -28,4 +28,6 @@
 \Ac*{arg}
 \iacsp{arg}
 
+$\mather{some text}$
+
 \end{document}
diff --git a/test/test-syntax/test-custom.vim b/test/test-syntax/test-custom.vim
index a6858dde47..0858aff76e 100644
--- a/test/test-syntax/test-custom.vim
+++ b/test/test-syntax/test-custom.vim
@@ -17,10 +17,21 @@ let g:vimtex_syntax_custom_cmds = [
       \ {'name': 'mygls', 'argspell': 0},
       \ {'name': 'slurp', 'argspell': 0, 'arggreedy': v:true},
       \ {'name': 'regex', 'cmdre': '[iI]?[aA]c[slaf]?p?\*?', 'conceal': 1},
+      \ {'name': 'mather', 'mathmode': 1,
+      \  'nextgroup': 'texMatherArg', 'hlgroup': 'texOpt'},
       \]
 
+call vimtex#syntax#add_to_mathzone_ignore('texMatherArg')
+
 EditConcealed test-custom.tex
 
+call vimtex#syntax#core#new_arg('texMatherArg', {
+      \ 'opts': 'contained keepend'
+      \})
+
 if empty($INMAKE) | finish | endif
 
+call assert_true(vimtex#syntax#in_mathzone(31, 5))
+call assert_false(vimtex#syntax#in_mathzone(31, 15))
+
 call vimtex#test#finished()