diff --git a/.changeset/tame-mails-act.md b/.changeset/tame-mails-act.md
new file mode 100644
index 00000000..fc5e7bef
--- /dev/null
+++ b/.changeset/tame-mails-act.md
@@ -0,0 +1,5 @@
+---
+'@supabase/auth-ui-svelte': patch
+---
+
+Make additionalData optional by default
diff --git a/packages/svelte/src/lib/Auth/Auth.svelte b/packages/svelte/src/lib/Auth/Auth.svelte
index 8287d603..2e926a2e 100644
--- a/packages/svelte/src/lib/Auth/Auth.svelte
+++ b/packages/svelte/src/lib/Auth/Auth.svelte
@@ -34,7 +34,7 @@
 	export let theme: 'default' | string = 'default';
 	export let localization: { variables?: I18nVariables } = {};
 	export let otpType: OtpType = 'email';
-	export let additionalData: { [key: string]: any } | undefined;
+	export let additionalData: { [key: string]: any } | undefined = undefined;
 
 	onMount(() => {
 		const { data: authListener } = supabaseClient.auth.onAuthStateChange((event) => {