diff --git a/balancer-js/src/lib/utils/coingecko-api.ts b/balancer-js/src/lib/utils/coingecko-api.ts
index cfedd2509..b56c42ab8 100644
--- a/balancer-js/src/lib/utils/coingecko-api.ts
+++ b/balancer-js/src/lib/utils/coingecko-api.ts
@@ -1,11 +1,11 @@
-export function getCoingeckoApiBaseUrl(isDemoApi = true) {
+export function getCoingeckoApiBaseUrl(isDemoApi = true): string {
   if (isDemoApi) {
     return 'https://api.coingecko.com/api/v3/';
   }
   return 'https://pro-api.coingecko.com/api/v3/';
 }
 
-export function getCoingeckoApiKeyHeaderName(isDemoApi = true) {
+export function getCoingeckoApiKeyHeaderName(isDemoApi = true): string {
   if (isDemoApi) {
     return 'x-cg-demo-api-key';
   }