diff --git a/app/src/lib/launchpad/first-buy.test.ts b/app/src/lib/launchpad/first-buy.test.ts
index cd853c00..7589d4f3 100644
--- a/app/src/lib/launchpad/first-buy.test.ts
+++ b/app/src/lib/launchpad/first-buy.test.ts
@@ -30,6 +30,10 @@ test("amountForUsd: short decimals parseUnits accepts, never more places than th
   assert.equal(amountForUsd(25, 1e12, 2), null, "rounds to nothing at 2 decimals");
   assert.equal(amountForUsd(0, 1, 6), null);
   assert.equal(amountForUsd(25, 0, 6), null);
+  assert.equal(amountForUsd(Infinity, 1, 18), null, "non-finite usd never becomes \"Infinity\" for parseUnits");
+  assert.equal(amountForUsd(NaN, 1, 18), null);
+  assert.equal(amountForUsd(25, Infinity, 18), null);
+  assert.equal(amountForUsd(25, NaN, 18), null);
   for (const [usd, dec] of [[2464.485, 18], [223.05, 18], [0.0000195, 18], [1, 6]] as const) {
     const a = amountForUsd(25, usd, dec)!;
     assert.ok(parseUnits(a, dec) > 0n, `parseUnits accepts ${a}`);
diff --git a/app/src/lib/launchpad/first-buy.ts b/app/src/lib/launchpad/first-buy.ts
index 759306cc..af0f0027 100644
--- a/app/src/lib/launchpad/first-buy.ts
+++ b/app/src/lib/launchpad/first-buy.ts
@@ -28,7 +28,7 @@ function trimZeros(s: string): string {
 
 /** `usd` worth of a quote priced at `quoteUsd`, as a short decimal string that parseUnits accepts; null when it rounds to nothing. */
 export function amountForUsd(usd: number, quoteUsd: number, decimals: number): string | null {
-  if (!(usd > 0) || !(quoteUsd > 0) || !Number.isFinite(quoteUsd)) return null;
+  if (!(usd > 0) || !(quoteUsd > 0) || !Number.isFinite(usd) || !Number.isFinite(quoteUsd)) return null;
   const v = usd / quoteUsd;
   let s = v >= 1 ? v.toFixed(2) : v.toPrecision(2);
   if (/e/i.test(s)) s = v.toFixed(Math.min(decimals, 12));