diff --git a/app/features/tournament/routes/to.$id.register.tsx b/app/features/tournament/routes/to.$id.register.tsx
index 3035e07c8..7b99e6cbc 100644
--- a/app/features/tournament/routes/to.$id.register.tsx
+++ b/app/features/tournament/routes/to.$id.register.tsx
@@ -82,7 +82,11 @@ export const action: ActionFunction = async ({ request, params }) => {
   const eventId = idFromParams(params);
   const event = notFoundIfFalsy(findByIdentifier(eventId));
 
-  invariant(event.isBeforeStart);
+  validate(
+    event.isBeforeStart,
+    400,
+    "Tournament has started, cannot make edits to registration"
+  );
 
   const teams = findTeamsByEventId(eventId);
   const ownTeam = teams.find((team) =>
diff --git a/app/utils/remix.ts b/app/utils/remix.ts
index 616f4b039..b35e7a9e3 100644
--- a/app/utils/remix.ts
+++ b/app/utils/remix.ts
@@ -94,10 +94,14 @@ function formDataToObject(formData: FormData) {
 
 /** Asserts condition is truthy. Throws a new `Response` with given status code if falsy.  */
 // eslint-disable-next-line @typescript-eslint/no-explicit-any -- same format as TS docs: https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#assertion-functions
-export function validate(condition: any, status = 400): asserts condition {
+export function validate(
+  condition: any,
+  status = 400,
+  body?: string
+): asserts condition {
   if (condition) return;
 
-  throw new Response(null, { status });
+  throw new Response(body, { status });
 }
 
 export type Breadcrumb =