diff --git a/client/src/lib/oauth-state-machine.ts b/client/src/lib/oauth-state-machine.ts
index 4a2c0f47..a5ae9d40 100644
--- a/client/src/lib/oauth-state-machine.ts
+++ b/client/src/lib/oauth-state-machine.ts
@@ -177,7 +177,7 @@ export const oauthTransitions: Record<OAuthStep, StateTransition> = {
         authorizationCode: context.state.authorizationCode,
         codeVerifier,
         redirectUri: context.provider.redirectUrl,
-        resource: context.state.resource ?? undefined,
+        resource: context.state.resource ? (context.state.resource instanceof URL ? context.state.resource : new URL(context.state.resource)) : undefined,
       });
 
       context.provider.saveTokens(tokens);