diff --git a/edgeless_api/src/function_instance/mod.rs b/edgeless_api/src/function_instance/mod.rs
index 69aae6f6..a418d424 100644
--- a/edgeless_api/src/function_instance/mod.rs
+++ b/edgeless_api/src/function_instance/mod.rs
@@ -2,6 +2,9 @@
 pub type NodeId = uuid::Uuid;
 pub type NodeLocalComponentId = uuid::Uuid;
 
+const NODE_ID_NONE: uuid::Uuid = uuid::uuid!("00000000-0000-0000-0000-fffe00000000");
+const FUNCTION_ID_NONE: uuid::Uuid = uuid::uuid!("00000000-0000-0000-0000-fffd00000000");
+
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct InstanceId {
     pub node_id: NodeId,
@@ -15,6 +18,12 @@ impl InstanceId {
             function_id: uuid::Uuid::new_v4(),
         }
     }
+    pub fn none() -> Self {
+        Self {
+            node_id: NODE_ID_NONE,
+            function_id: FUNCTION_ID_NONE,
+        }
+    }
 }
 
 #[derive(Debug, Clone)]
diff --git a/edgeless_cli/src/edgeless_cli.rs b/edgeless_cli/src/edgeless_cli.rs
index b7bb9a56..7ff6210a 100644
--- a/edgeless_cli/src/edgeless_cli.rs
+++ b/edgeless_cli/src/edgeless_cli.rs
@@ -229,19 +229,13 @@ async fn main() -> anyhow::Result<()> {
                             node_id: uuid::Uuid::parse_str(&node_id)?,
                             function_id: uuid::Uuid::parse_str(&function_id)?,
                         },
-                        source: edgeless_api::function_instance::InstanceId {
-                            node_id: uuid::uuid!("00000000-0000-0000-0000-ffff00000000"),
-                            function_id: uuid::uuid!("00000000-0000-0000-0000-ffff00000000"),
-                        },
+                        source: edgeless_api::function_instance::InstanceId::none(),
                         stream_id: 0,
                         data: match event_type.as_str() {
                             "cast" => edgeless_api::invocation::EventData::Cast(payload),
-                            _ => edgeless_api::invocation::EventData::Err,
+                            _ => return Err(anyhow::anyhow!("invalid event type: {}", event_type)),
                         },
                     };
-                    if let edgeless_api::invocation::EventData::Err = event.data {
-                        return Err(anyhow::anyhow!("invalid event type: {}", event_type));
-                    }
                     match edgeless_api::invocation::InvocationAPI::handle(&mut client, event).await {
                         Ok(_) => println!("event casted"),
                         Err(err) => return Err(anyhow::anyhow!("error casting the event: {}", err)),