diff --git a/internal/cli/server/api_service.go b/internal/cli/server/api_service.go
index 3781b6b45d..5af1a4adf6 100644
--- a/internal/cli/server/api_service.go
+++ b/internal/cli/server/api_service.go
@@ -49,6 +49,10 @@ func (s *Server) HeaderByNumber(ctx context.Context, req *protobor.GetHeaderByNu
 		return nil, err
 	}
 
+	if header == nil {
+		return nil, errors.New("header not found")
+	}
+
 	return &protobor.GetHeaderByNumberResponse{Header: headerToProtoborHeader(header)}, nil
 }
 
@@ -62,6 +66,10 @@ func (s *Server) BlockByNumber(ctx context.Context, req *protobor.GetBlockByNumb
 		return nil, err
 	}
 
+	if block == nil {
+		return nil, errors.New("block not found")
+	}
+
 	return &protobor.GetBlockByNumberResponse{Block: blockToProtoBlock(block)}, nil
 }