diff --git a/models/src/jrpc.rs b/models/src/jrpc.rs
index 8719aae..88e7564 100644
--- a/models/src/jrpc.rs
+++ b/models/src/jrpc.rs
@@ -103,7 +103,7 @@ pub struct GetBlockchainConfigResponse {
     pub global_id: i32,
     #[serde(with = "serde_ton_block")]
     pub config: ton_block::ConfigParams,
-    pub seqno: u32,
+    pub seqno: Option<u32>,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
diff --git a/server/src/jrpc.rs b/server/src/jrpc.rs
index 99a5316..ed57bd8 100644
--- a/server/src/jrpc.rs
+++ b/server/src/jrpc.rs
@@ -67,7 +67,7 @@ impl JrpcServer {
             let config_response = serde_json::to_value(jrpc::GetBlockchainConfigResponse {
                 global_id: block.global_id,
                 config: config.clone(),
-                seqno,
+                seqno: Some(seqno),
             })?;
 
             Ok((Arc::new(key_block_response), Arc::new(config_response)))