diff --git a/crates/caldav/src/calendar/resource.rs b/crates/caldav/src/calendar/resource.rs
index a2e999a..e78772d 100644
--- a/crates/caldav/src/calendar/resource.rs
+++ b/crates/caldav/src/calendar/resource.rs
@@ -79,7 +79,8 @@ pub enum CalendarProp {
     // Collection Synchronization (RFC 6578)
     SyncToken(String),
 
-    // Didn't find the spec
+    // CalendarServer
+    #[serde(rename = "CS:getctag", alias = "getctag")]
     Getctag(String),
 
     #[serde(other)]