diff --git a/luamml-convert.lua b/luamml-convert.lua
index f675339..a90f779 100644
--- a/luamml-convert.lua
+++ b/luamml-convert.lua
@@ -636,6 +636,7 @@ end
 
 return {
   register_family = register_remap,
+  register_text_family = function(fam) text_families[fam] = true end,
   process = function(head, style) return nodes_to_table(head, style or 2) end,
   make_root = to_math,
 }
diff --git a/luamml-tex.lua b/luamml-tex.lua
index 4febba1..b69be9b 100644
--- a/luamml-tex.lua
+++ b/luamml-tex.lua
@@ -2,6 +2,7 @@ local mlist_to_mml = require'luamml-convert'
 local process_mlist = mlist_to_mml.process
 local make_root = mlist_to_mml.make_root
 local register_family = mlist_to_mml.register_family
+local register_text_family = mlist_to_mml.register_text_family
 
 local mappings = require'luamml-legacy-mappings'
 local write_xml = require'luamml-xmlwriter'
@@ -23,6 +24,14 @@ lua.get_functions_table()[funcid] = function()
   end
 end
 
+local funcid = luatexbase.new_luafunction'RegisterFamilyMapping'
+token.set_lua('RegisterTextFamily', funcid, 'protected')
+lua.get_functions_table()[funcid] = function()
+  local fam = token.scan_int()
+  local kind = token.scan_string()
+  register_text_family(fam, kind)
+end
+
 local function shallow_copy(t)
   local tt = {}
   for k,v in next, t do