diff --git a/src/utils/ethereum.ts b/src/utils/ethereum.ts
index a2283b7..86b4a3a 100644
--- a/src/utils/ethereum.ts
+++ b/src/utils/ethereum.ts
@@ -4,7 +4,7 @@ export const normalizeTransactionResponsePayload = (
   payload: TransactionResponse,
 ): TransactionResponse => {
   // Firefox can't serialize functions
-  if (navigator.userAgent.toLowerCase().includes('firefox')) {
+  if (navigator.userAgent?.toLowerCase().includes('firefox')) {
     // eslint-disable-next-line @typescript-eslint/no-unused-vars
     const { wait: _, ...cleanedPayload } = payload;
     return cleanedPayload as TransactionResponse;