diff --git a/src/runtime2/component/component.rs b/src/runtime2/component/component.rs
index cddd244fa3f52157eb6ff24e617dd061daf02408..e47f44029bfdc991f9b827a18734ad3971c3a7d9 100644
--- a/src/runtime2/component/component.rs
+++ b/src/runtime2/component/component.rs
@@ -285,6 +285,8 @@ pub(crate) fn default_handle_incoming_data_message(
 ) -> IncomingData {
     let port_handle = comp_ctx.get_port_handle(incoming_message.data_header.target_port);
     let port_index = comp_ctx.get_port_index(port_handle);
+    sched_ctx.log("DEBUG: Setting received_message_for_sync");
+    comp_ctx.get_port_mut(port_handle).received_message_for_sync = true;
     let port_value_slot = &mut inbox_main[port_index];
     let target_port_id = incoming_message.data_header.target_port;
 
@@ -368,7 +370,8 @@ pub(crate) fn default_attempt_get(
         }
     } else {
         // We don't have a message waiting for us.
-        let port_info = comp_ctx.get_port(port_handle);
+        let port_info = comp_ctx.get_port_mut(port_handle);
+        port_info.last_instruction = target_port_instruction;
         let port_is_closed = port_info.state == PortState::Closed;
         if port_is_closed {
             let peer_id = port_info.peer_comp_id;
@@ -499,11 +502,13 @@ pub(crate) fn default_handle_control_message(
                 // now it is in the `BlockedGet` state.
                 let port_was_used = last_instruction != PortInstruction::None;
 
+                sched_ctx.log(&format!("DEBUG: last_instruction = {:?}, mode = {:?}, was_used = {}, has_had_message = {}", last_instruction, exec_state.mode, port_was_used, port_has_had_message));
+
                 if exec_state.mode.is_in_sync_block() {
                     let closed_during_sync_round = content.closed_in_sync_round && port_was_used;
-                    // TODO: Finish this
+                    let closed_before_sync_round = !content.closed_in_sync_round && !port_has_had_message;
 
-                    if closed_during_sync_round {
+                    if closed_during_sync_round || closed_before_sync_round {
                         return Err((
                             last_instruction,
                             format!("Peer component (id:{}) shut down, so previous communication cannot have succeeded", peer_comp_id.0)
@@ -618,7 +623,7 @@ pub(crate) fn default_handle_start_exit(
     // Iterating over ports by index to work around borrowing rules
     for port_index in 0..comp_ctx.num_ports() {
         let port = comp_ctx.get_port_by_index_mut(port_index);
-        if port.state == PortState::Closed {
+        if port.state == PortState::Closed || port.close_at_sync_end {
             // Already closed, or in the process of being closed
             continue;
         }