diff --git a/rust/src/events/formats/vmsc4242.rs b/rust/src/events/formats/vmsc4242.rs
index 46bf459d83..896d479358 100644
--- a/rust/src/events/formats/vmsc4242.rs
+++ b/rust/src/events/formats/vmsc4242.rs
@@ -87,7 +87,7 @@ impl EventFormatVMSC4242 {
             && auth_event_ids.is_empty()
         {
             return Err(PyAssertionError::new_err(format!(
-                "auth_event_ids has not been calculated : {}",
+                "auth_event_ids has not been calculated for event_id='{}'. This is most likely a Synapse programming error.",
                 event.event_id
             )));
         }