diff --git a/src/runtime2/communication.rs b/src/runtime2/communication.rs
index cebb7b67d319eb1fb2106c9ac06857d5a575659f..7be0b8b8ec97bb4981dccfaab90c50de37fcba94 100644
--- a/src/runtime2/communication.rs
+++ b/src/runtime2/communication.rs
@@ -176,11 +176,17 @@ pub enum ControlMessageContent {
     Ack,
     BlockPort(PortId),
     UnblockPort(PortId),
-    ClosePort(PortId),
+    ClosePort(ControlMessageClosePort),
     PortPeerChangedBlock(PortId),
     PortPeerChangedUnblock(PortId, CompId),
 }
 
+#[derive(Debug)]
+pub struct ControlMessageClosePort {
+    pub port_to_close: PortId, // ID of the receiving port
+    pub closed_in_sync_round: bool, // needed to ensure correct handling of errors
+}
+
 // -----------------------------------------------------------------------------
 // Messages (generic)
 // -----------------------------------------------------------------------------