src/Tools/Code/code_ml.ML

             (print_val_decl print_dicttypscheme
               (inst, (vs, (class, tyco `%% map (ITyVar o fst) vs))))
             (concat (
               str definer
               :: (str o deresolve) inst
-              :: print_dict_args vs
+              :: (if is_pseudo_fun inst then [str "()"]
+                  else print_dict_args vs)
               @ str "="
               @@ brackets [
                 enum_default "()" ";" "{" "}" (map print_super_instance super_instances
                   @ map print_classparam_instance classparam_instances),
                 str ":",