diff --git a/src/javascript/app/common/active_symbols.js b/src/javascript/app/common/active_symbols.js
index 4959fa3a39bfe..cdafd3a1cfba7 100644
--- a/src/javascript/app/common/active_symbols.js
+++ b/src/javascript/app/common/active_symbols.js
@@ -26,7 +26,7 @@ const submarket_order = {
 };
 
 const ActiveSymbols = (() => {
-    const groupBy = (xs, key) => (
+    const groupBy = (xs = [], key) => (
         xs.reduce((rv, x) => {
             (rv[x[key]] = rv[x[key]] || []).push(x);
             return rv;