diff --git a/src/LoginPage.tsx b/src/LoginPage.tsx
index 4c3d5d9..5a8727d 100644
--- a/src/LoginPage.tsx
+++ b/src/LoginPage.tsx
@@ -41,7 +41,7 @@ export default function LoginPage() {
       setLoading(true);
       setFetchError(undefined);
       const etebase = await startTask((async () => {
-        return await Etebase.Account.login(username, password, serviceApiUrl);
+        return await Etebase.Account.login(username, password, serviceApiUrl ?? C.defaultServerUrl);
       }));
       dispatch(login(etebase));
     } catch (e) {
diff --git a/src/SignupPage.tsx b/src/SignupPage.tsx
index e99435c..e747eac 100644
--- a/src/SignupPage.tsx
+++ b/src/SignupPage.tsx
@@ -87,7 +87,7 @@ export default function SignupPage() {
         setErrors({});
       }
 
-      const serverUrl = (showAdvanced) ? server : undefined;
+      const serverUrl = (showAdvanced) ? server : C.defaultServerUrl;
       const user: Etebase.User = {
         username,
         email,