diff --git a/lib/kalshi/rest.js b/lib/kalshi/rest.js
index 1f9aa4e..ae19d72 100644
--- a/lib/kalshi/rest.js
+++ b/lib/kalshi/rest.js
@@ -1,5 +1,6 @@
 import { signRequest, KALSHI_API_BASE } from './auth.js';
 
+const SERIES_TICKER = 'KXBTC15M';
 const OPEN_EVENT_STATUSES = new Set(['open', 'active', 'initialized', 'trading']);
 
 async function kalshiFetch(method, path, body = null) {
@@ -68,8 +69,7 @@ async function fetchEvents(series, query) {
  * Returns the currently active event + its markets.
  */
 export async function getActiveBTCEvent() {
-  const configuredSeries = process.env.KALSHI_SERIES_TICKER || 'KXBTC15M';
-  const seriesCandidates = [...new Set([configuredSeries, configuredSeries.toUpperCase(), configuredSeries.toLowerCase()])];
+  const seriesCandidates = [...new Set([SERIES_TICKER, SERIES_TICKER.toLowerCase()])];
   const eventMap = new Map();
 
   for (const series of seriesCandidates) {