diff --git a/core/services/relay/evm/mercury/wsrpc/client.go b/core/services/relay/evm/mercury/wsrpc/client.go
index 06e30c1e0ef..1aa674f1958 100644
--- a/core/services/relay/evm/mercury/wsrpc/client.go
+++ b/core/services/relay/evm/mercury/wsrpc/client.go
@@ -384,11 +384,13 @@ func (w *client) Transmit(ctx context.Context, req *pb.TransmitRequest) (resp *p
 		return nil, errors.Wrap(err, "Transmit call failed")
 	}
 
-	signature, err := w.Sign(req)
-	if err != nil {
-		return nil, errors.Wrap(err, "Transmit call failed")
+	if w.tlsCertFile != nil {
+		signature, err := w.Sign(req)
+		if err != nil {
+			return nil, errors.Wrap(err, "Transmit call failed")
+		}
+		ctx = metadata.AppendToOutgoingContext(ctx, "csa-key", w.csaKey.PublicKeyString(), "signature", signature)
 	}
-	ctx = metadata.AppendToOutgoingContext(ctx, "csa-key", w.csaKey.PublicKeyString(), "signature", signature)
 	resp, err = w.rawClient.Transmit(ctx, req)
 	w.handleTimeout(err)
 	if err != nil {
@@ -442,11 +444,13 @@ func (w *client) LatestReport(ctx context.Context, req *pb.LatestReportRequest)
 		return nil, errors.Wrap(err, "LatestReport failed")
 	}
 
-	signature, err := w.Sign(req)
-	if err != nil {
-		return nil, errors.Wrap(err, "Transmit call failed")
+	if w.tlsCertFile != nil {
+		signature, err := w.Sign(req)
+		if err != nil {
+			return nil, errors.Wrap(err, "Transmit call failed")
+		}
+		ctx = metadata.AppendToOutgoingContext(ctx, "csa-key", w.csaKey.PublicKeyString(), "signature", signature)
 	}
-	ctx = metadata.AppendToOutgoingContext(ctx, "csa-key", w.csaKey.PublicKeyString(), "signature", signature)
 	var cached bool
 	if w.cache == nil {
 		resp, err = w.rawClient.LatestReport(ctx, req)