diff --git a/lib/rdma_provider/rdma_provider_mlx5_dv.c b/lib/rdma_provider/rdma_provider_mlx5_dv.c
index 2ede3797173..f7710139fd0 100644
--- a/lib/rdma_provider/rdma_provider_mlx5_dv.c
+++ b/lib/rdma_provider/rdma_provider_mlx5_dv.c
@@ -23,6 +23,33 @@ struct spdk_rdma_mlx5_dv_qp {
 	struct ibv_qp_ex *qpex;
 };
 
+/*
+ * rdma_set_option(RDMA_OPTION_ID_TOS) programs SL (SQ / tx_prio). mlx5_dv
+ * moves the QP itself via ibv_modify_qp, so ConnectX builds the RoCEv2
+ * IPv4 header from the RTR AV traffic_class — which rdma_init_qp_attr
+ * often leaves 0. Fill TOS = SL<<5 (CS DSCP) when the AV is present and
+ * traffic_class is unset.
+ */
+static void
+rdma_mlx5_dv_fill_roce_tos(struct ibv_qp_attr *qp_attr, int qp_attr_mask)
+{
+	uint8_t sl;
+
+	if ((qp_attr_mask & IBV_QP_AV) == 0) {
+		return;
+	}
+	if (qp_attr->ah_attr.grh.traffic_class != 0) {
+		return;
+	}
+
+	sl = qp_attr->ah_attr.sl;
+	if (sl == 0) {
+		return;
+	}
+
+	qp_attr->ah_attr.grh.traffic_class = sl << 5;
+}
+
 static int
 rdma_mlx5_dv_init_qpair(struct spdk_rdma_mlx5_dv_qp *mlx5_qp)
 {
@@ -49,6 +76,8 @@ rdma_mlx5_dv_init_qpair(struct spdk_rdma_mlx5_dv_qp *mlx5_qp)
 		return rc;
 	}
 
+	rdma_mlx5_dv_fill_roce_tos(&qp_attr, qp_attr_mask);
+
 	rc = ibv_modify_qp(mlx5_qp->common.qp, &qp_attr, qp_attr_mask);
 	if (rc) {
 		SPDK_ERRLOG("ibv_modify_qp(IBV_QPS_RTR) failed, rc %d\n", rc);