diff --git a/crates/frontend/js-components/lib/create-calendar-form.ts b/crates/frontend/js-components/lib/create-calendar-form.ts
index a65bb85..adfec17 100644
--- a/crates/frontend/js-components/lib/create-calendar-form.ts
+++ b/crates/frontend/js-components/lib/create-calendar-form.ts
@@ -103,7 +103,7 @@ export class CreateCalendarForm extends LitElement {
             <displayname>${this.displayname}</displayname>
             ${this.description ? `<CAL:calendar-description>${this.description}</CAL:calendar-description>` : ''}
             ${this.color ? `<ICAL:calendar-color>${this.color}</ICAL:calendar-color>` : ''}
-            ${this.subscriptionUrl ? `<CS:source>${this.subscriptionUrl}</CS:source>` : ''}
+            ${this.subscriptionUrl ? `<CS:source><href>${this.subscriptionUrl}</href></CS:source>` : ''}
             <CAL:supported-calendar-component-set>
               ${Array.from(this.components.keys()).map(comp => `<CAL:comp name="${comp}" />`).join('\n')}
             </CAL:supported-calendar-component-set>
diff --git a/crates/frontend/public/assets/js/create-calendar-form.mjs b/crates/frontend/public/assets/js/create-calendar-form.mjs
index ca9d6e0..dc62b23 100644
--- a/crates/frontend/public/assets/js/create-calendar-form.mjs
+++ b/crates/frontend/public/assets/js/create-calendar-form.mjs
@@ -81,7 +81,7 @@ let r = class extends u {
             <displayname>${this.displayname}</displayname>
             ${this.description ? `<CAL:calendar-description>${this.description}</CAL:calendar-description>` : ""}
             ${this.color ? `<ICAL:calendar-color>${this.color}</ICAL:calendar-color>` : ""}
-            ${this.subscriptionUrl ? `<CS:source>${this.subscriptionUrl}</CS:source>` : ""}
+            ${this.subscriptionUrl ? `<CS:source><href>${this.subscriptionUrl}</href></CS:source>` : ""}
             <CAL:supported-calendar-component-set>
               ${Array.from(this.components.keys()).map((e) => `<CAL:comp name="${e}" />`).join(`
 `)}