diff --git a/lean_client/networking/src/network/service.rs b/lean_client/networking/src/network/service.rs
index a0a188d..5b469cf 100644
--- a/lean_client/networking/src/network/service.rs
+++ b/lean_client/networking/src/network/service.rs
@@ -41,9 +41,11 @@ use crate::{
     discovery::{DiscoveryConfig, DiscoveryService},
     enr_ext::EnrExt,
     gossipsub::{self, config::GossipsubConfig, message::GossipsubMessage, topic::GossipsubKind},
-    network::behaviour::{LeanNetworkBehaviour, LeanNetworkBehaviourEvent},
-    network::range_sync::{MAX_SYNC_RANGE, RangeSyncState},
-    req_resp::{self, LeanRequest, ReqRespMessage},
+    network::{
+        behaviour::{LeanNetworkBehaviour, LeanNetworkBehaviourEvent},
+        range_sync::{MAX_SYNC_RANGE, RangeSyncState},
+    },
+    req_resp::{self, LeanRequest, RESPONSE_INVALID_REQUEST, ReqRespMessage},
     types::{
         CanonicalBlocksProvider, ChainMessage, ChainMessageSink, ConnectionState,
         MAX_BLOCK_CACHE_SIZE, NetworkFinalizedSlot, OutboundP2pRequest, P2pRequestSource,
@@ -1676,8 +1678,10 @@ where
 
                     if count == 0 || count > req_resp::MAX_REQUEST_BLOCKS as u64 {
                         info!(peer = %peer, start_slot, count, "Rejecting BlocksByRange: invalid count");
-                        // Send an empty response — peer will treat as no data.
-                        let response = LeanResponse::BlocksByRange(Vec::new());
+                        let response = LeanResponse::Error {
+                            code: RESPONSE_INVALID_REQUEST,
+                            message: "Invalid Block Request Count".to_string(),
+                        };
                         if let Err(e) = self
                             .swarm
                             .behaviour_mut()
diff --git a/lean_client/networking/src/req_resp.rs b/lean_client/networking/src/req_resp.rs
index 8e359a7..fb6026c 100644
--- a/lean_client/networking/src/req_resp.rs
+++ b/lean_client/networking/src/req_resp.rs
@@ -62,6 +62,7 @@ pub enum LeanResponse {
     Status(Status),
     BlocksByRoot(Vec<SignedBlock>),
     BlocksByRange(Vec<SignedBlock>),
+    Error { code: u8, message: String },
     Empty,
 }
 
@@ -297,6 +298,9 @@ impl LeanCodec {
                 }
                 Ok(result)
             }
+            LeanResponse::Error { code, message } => {
+                Self::encode_response_chunk(*code, message.as_bytes())
+            }
             LeanResponse::Empty => Ok(Vec::new()),
         }
     }