diff --git a/play.pokemonshowdown.com/src/panel-mainmenu.tsx b/play.pokemonshowdown.com/src/panel-mainmenu.tsx
index 297fa05ee8..22bed2e9b9 100644
--- a/play.pokemonshowdown.com/src/panel-mainmenu.tsx
+++ b/play.pokemonshowdown.com/src/panel-mainmenu.tsx
@@ -818,10 +818,12 @@ export class TeamForm extends preact.Component<{
 	submit = (ev: Event, validate?: 'validate') => {
 		ev.preventDefault();
 		const format = this.format;
+		// in tournaments, format is the custom name & teamFormat is the original format.
+		const teambuilderFormat = this.props.teamFormat;
 		const teamElement = this.base!.querySelector<HTMLButtonElement>('button[name=team]');
 		const teamKey = teamElement!.value;
 		const team = teamKey ? PS.teams.byKey[teamKey] : undefined;
-		if (!window.BattleFormats[PS.teams.teambuilderFormat(format)]?.team && !team) {
+		if (!window.BattleFormats[teambuilderFormat || PS.teams.teambuilderFormat(format)]?.team && !team) {
 			PS.alert('You need to go into the Teambuilder and build a team for this format.', {
 				parentElem: teamElement!,
 			});