diff --git a/src/stores/auth.ts b/src/stores/auth.ts
index 1430139..4a6b7e9 100644
--- a/src/stores/auth.ts
+++ b/src/stores/auth.ts
@@ -63,13 +63,13 @@ export const useAuthStore = create<AuthState>()(
 
           // Step 2: WebAuthn ceremony
           const publicKeyOptions: PublicKeyCredentialRequestOptions = {
-            challenge: fromBase64url(options.challenge),
+            challenge: fromBase64url(options.challenge).buffer as ArrayBuffer,
             rpId: options.rpId,
             userVerification: options.userVerification as UserVerificationRequirement,
             timeout: options.timeout,
             allowCredentials: options.allowCredentials?.map((c: any) => ({
               type: c.type as PublicKeyCredentialType,
-              id: fromBase64url(c.id),
+              id: fromBase64url(c.id).buffer as ArrayBuffer,
               transports: c.transports as AuthenticatorTransport[],
             })),
           };
@@ -124,10 +124,10 @@ export const useAuthStore = create<AuthState>()(
 
           // Step 2: WebAuthn ceremony
           const publicKeyOptions: PublicKeyCredentialCreationOptions = {
-            challenge: fromBase64url(options.challenge),
+            challenge: fromBase64url(options.challenge).buffer as ArrayBuffer,
             rp: options.rp,
             user: {
-              id: fromBase64url(options.user.id),
+              id: fromBase64url(options.user.id).buffer as ArrayBuffer,
               name: options.user.name,
               displayName: options.user.displayName,
             },