diff --git a/web/src/billing/sponsorship.ts b/web/src/billing/sponsorship.ts
index 6b99aefd18..ad2537a875 100644
--- a/web/src/billing/sponsorship.ts
+++ b/web/src/billing/sponsorship.ts
@@ -1,4 +1,5 @@
 import $ from "jquery";
+import assert from "minimalistic-assert";
 import {z} from "zod";
 
 import * as helpers from "./helpers";
@@ -19,18 +20,21 @@ function hide_submit_loading_indicator(): void {
 
 function validate_data(data: helpers.FormDataObject): boolean {
     let found_error = false;
+    assert(data.description !== undefined);
     if (data.description.trim() === "") {
         $("#sponsorship-description-error").text("Organization description cannot be blank.");
         hide_submit_loading_indicator();
         found_error = true;
     }
 
+    assert(data.paid_users_count !== undefined);
     if (data.paid_users_count.trim() === "") {
         $("#sponsorship-paid-users-count-error").text("Number of paid staff cannot be blank.");
         hide_submit_loading_indicator();
         found_error = true;
     }
 
+    assert(data.expected_total_users !== undefined);
     if (data.expected_total_users.trim() === "") {
         $("#sponsorship-expected-total-users-error").text(
             "Expected number of users cannot be blank.",