diff --git a/linera-core/src/unit_tests/client_tests.rs b/linera-core/src/unit_tests/client_tests.rs
index 1d70c0ad649..b66b8e7282a 100644
--- a/linera-core/src/unit_tests/client_tests.rs
+++ b/linera-core/src/unit_tests/client_tests.rs
@@ -511,6 +511,26 @@ where
         .await
         .unwrap()
         .unwrap();
+
+    // Regression test for #2869.
+    let sub_message_id = MessageId {
+        index: message_id.index + 1,
+        ..message_id
+    };
+    assert_matches!(
+        certificate.executed_block().messages()[0][sub_message_id.index as usize].message,
+        Message::System(SystemMessage::Subscribe { .. })
+    );
+    assert_eq!(
+        sender
+            .client
+            .local_node()
+            .certificate_for(&sub_message_id)
+            .await
+            .unwrap(),
+        certificate.clone().into()
+    );
+
     assert_eq!(sender.next_block_height(), BlockHeight::from(1));
     assert!(sender.pending_block().is_none());
     assert!(sender.key_pair().await.is_ok());