diff -r 3f371ba2b4fc -r 304f22435bc7 src/HOL/Tools/ATP/atp_problem_generate.ML
--- a/src/HOL/Tools/ATP/atp_problem_generate.ML	Thu Aug 19 14:23:47 2021 +0200
+++ b/src/HOL/Tools/ATP/atp_problem_generate.ML	Fri Aug 20 17:57:57 2021 +0200
@@ -1528,7 +1528,8 @@
     (make_fixed_const NONE \<^const_name>\<open>undefined\<close>, mk_sym_info false 0) ::
     (map (rpair (mk_sym_info true 0)) [tptp_false, tptp_true]) @
     (map (rpair (mk_sym_info true 1)) tptp_unary_builtins) @
-    (map (rpair (mk_sym_info true 2)) (tptp_old_equal :: tptp_binary_builtins))
+    (map (rpair (mk_sym_info true 2)) (tptp_old_equal :: tptp_binary_builtins)) @
+    (map (rpair (mk_sym_info true 3)) tptp_ternary_builtins)
     |> not (is_type_enc_fool type_enc orelse is_type_enc_full_higher_order type_enc)
       ? cons (prefixed_predicator_name, mk_sym_info true 1)
   end