diff --git a/src/cache.rs b/src/cache.rs
index 679a37c..dea0d55 100644
--- a/src/cache.rs
+++ b/src/cache.rs
@@ -183,12 +183,13 @@ impl CalDavSource<CachedCalendar> for Cache {
         self.data.calendars.get(id).map(|arc| arc.clone())
     }
 
-    async fn insert_calendar(&mut self, new_calendar: CachedCalendar) -> Result<(), Box<dyn Error>> {
+    async fn insert_calendar(&mut self, new_calendar: CachedCalendar) -> Result<Arc<Mutex<CachedCalendar>>, Box<dyn Error>> {
         let id = new_calendar.id().clone();
         log::debug!("Inserting local calendar {}", id);
-        match self.data.calendars.insert(id, Arc::new(Mutex::new(new_calendar))) {
+        let arc = Arc::new(Mutex::new(new_calendar));
+        match self.data.calendars.insert(id, arc.clone()) {
             Some(_) => Err("Attempt to insert calendar failed: there is alredy such a calendar.".into()),
-            None => Ok(()) ,
+            None => Ok(arc) ,
         }
     }
 }
diff --git a/src/client.rs b/src/client.rs
index 81bc81a..59ca993 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -231,8 +231,8 @@ impl CalDavSource<RemoteCalendar> for Client {
             .map(|cal| cal.clone())
         }
 
-    async fn insert_calendar(&mut self, new_calendar: RemoteCalendar) -> Result<(), Box<dyn Error>> {
-        Err("Not implemented".into())
+    async fn insert_calendar(&mut self, _new_calendar: RemoteCalendar) -> Result<Arc<Mutex<RemoteCalendar>>, Box<dyn Error>> {
+        todo!();
     }
 }
 
diff --git a/src/traits.rs b/src/traits.rs
index 74859b2..1942a70 100644
--- a/src/traits.rs
+++ b/src/traits.rs
@@ -17,8 +17,8 @@ pub trait CalDavSource<T: BaseCalendar> {
     async fn get_calendars(&self) -> Result<HashMap<CalendarId, Arc<Mutex<T>>>, Box<dyn Error>>;
     /// Returns the calendar matching the ID
     async fn get_calendar(&self, id: &CalendarId) -> Option<Arc<Mutex<T>>>;
-    /// Insert a calendar if it did not exist
-    async fn insert_calendar(&mut self, new_calendar: T) -> Result<(), Box<dyn Error>>;
+    /// Insert a calendar if it did not exist, and return it
+    async fn insert_calendar(&mut self, new_calendar: T) -> Result<Arc<Mutex<T>>, Box<dyn Error>>;
 }
 
 /// This trait contains functions that are common to all calendars