diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
index 05f66f7b6..6e44d5ff0 100644
--- a/drivers/net/mlx5/mlx5_ethdev.c
+++ b/drivers/net/mlx5/mlx5_ethdev.c
@@ -377,15 +377,15 @@ mlx5_dev_configure(struct rte_eth_dev *dev)
 
 	if (use_app_rss_key &&
 	    (dev->data->dev_conf.rx_adv_conf.rss_conf.rss_key_len !=
-	     rss_hash_default_key_len)) {
-		DRV_LOG(ERR, "port %u RSS key len must be %zu Bytes long",
-			dev->data->port_id, rss_hash_default_key_len);
+	     MLX5_RSS_HASH_KEY_LEN)) {
+		DRV_LOG(ERR, "port %u RSS key len must be %s Bytes long",
+			dev->data->port_id, RTE_STR(MLX5_RSS_HASH_KEY_LEN));
 		rte_errno = EINVAL;
 		return -rte_errno;
 	}
 	priv->rss_conf.rss_key =
 		rte_realloc(priv->rss_conf.rss_key,
-			    rss_hash_default_key_len, 0);
+			    MLX5_RSS_HASH_KEY_LEN, 0);
 	if (!priv->rss_conf.rss_key) {
 		DRV_LOG(ERR, "port %u cannot allocate RSS hash key memory (%u)",
 			dev->data->port_id, rxqs_n);
@@ -396,8 +396,8 @@ mlx5_dev_configure(struct rte_eth_dev *dev)
 	       use_app_rss_key ?
 	       dev->data->dev_conf.rx_adv_conf.rss_conf.rss_key :
 	       rss_hash_default_key,
-	       rss_hash_default_key_len);
-	priv->rss_conf.rss_key_len = rss_hash_default_key_len;
+	       MLX5_RSS_HASH_KEY_LEN);
+	priv->rss_conf.rss_key_len = MLX5_RSS_HASH_KEY_LEN;
 	priv->rss_conf.rss_hf = dev->data->dev_conf.rx_adv_conf.rss_conf.rss_hf;
 	priv->rxqs = (void *)dev->data->rx_queues;
 	priv->txqs = (void *)dev->data->tx_queues;
@@ -515,7 +515,7 @@ mlx5_dev_infos_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *info)
 		info->if_index = if_nametoindex(ifname);
 	info->reta_size = priv->reta_idx_n ?
 		priv->reta_idx_n : config->ind_table_max_size;
-	info->hash_key_size = rss_hash_default_key_len;
+	info->hash_key_size = MLX5_RSS_HASH_KEY_LEN;
 	info->speed_capa = priv->link_speed_capa;
 	info->flow_type_rss_offloads = ~MLX5_RSS_HF_MASK;
 	mlx5_set_default_params(dev, info);
diff --git a/drivers/net/mlx5/mlx5_flow.c b/drivers/net/mlx5/mlx5_flow.c
index 1280db486..77483bd1f 100644
--- a/drivers/net/mlx5/mlx5_flow.c
+++ b/drivers/net/mlx5/mlx5_flow.c
@@ -1493,11 +1493,11 @@ mlx5_flow_apply(struct rte_eth_dev *dev, struct rte_flow *flow,
 		struct mlx5_hrxq *hrxq;
 
 		hrxq = mlx5_hrxq_get(dev, rss_hash_default_key,
-				     rss_hash_default_key_len, 0,
+				     MLX5_RSS_HASH_KEY_LEN, 0,
 				     &flow->queue, 1, 0, 0);
 		if (!hrxq)
 			hrxq = mlx5_hrxq_new(dev, rss_hash_default_key,
-					     rss_hash_default_key_len, 0,
+					     MLX5_RSS_HASH_KEY_LEN, 0,
 					     &flow->queue, 1, 0, 0);
 		if (!hrxq)
 			return rte_flow_error_set(error, rte_errno,
diff --git a/drivers/net/mlx5/mlx5_prm.h b/drivers/net/mlx5/mlx5_prm.h
index f9fae1e50..0870d32fd 100644
--- a/drivers/net/mlx5/mlx5_prm.h
+++ b/drivers/net/mlx5/mlx5_prm.h
@@ -21,6 +21,9 @@
 #include <rte_vect.h>
 #include "mlx5_autoconf.h"
 
+/* RSS hash key size. */
+#define MLX5_RSS_HASH_KEY_LEN 40
+
 /* Get CQE owner bit. */
 #define MLX5_CQE_OWNER(op_own) ((op_own) & MLX5_CQE_OWNER_MASK)
 
diff --git a/drivers/net/mlx5/mlx5_rss.c b/drivers/net/mlx5/mlx5_rss.c
index d69b4c09e..b95778a8c 100644
--- a/drivers/net/mlx5/mlx5_rss.c
+++ b/drivers/net/mlx5/mlx5_rss.c
@@ -50,10 +50,11 @@ mlx5_rss_hash_update(struct rte_eth_dev *dev,
 		return -rte_errno;
 	}
 	if (rss_conf->rss_key && rss_conf->rss_key_len) {
-		if (rss_conf->rss_key_len != rss_hash_default_key_len) {
+		if (rss_conf->rss_key_len != MLX5_RSS_HASH_KEY_LEN) {
 			DRV_LOG(ERR,
-				"port %u RSS key len must be %zu Bytes long",
-				dev->data->port_id, rss_hash_default_key_len);
+				"port %u RSS key len must be %s Bytes long",
+				dev->data->port_id,
+				RTE_STR(MLX5_RSS_HASH_KEY_LEN));
 			rte_errno = EINVAL;
 			return -rte_errno;
 		}
diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index d960daa43..d50b82c69 100644
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -52,7 +52,9 @@ uint8_t rss_hash_default_key[] = {
 };
 
 /* Length of the default RSS hash key. */
-const size_t rss_hash_default_key_len = sizeof(rss_hash_default_key);
+static_assert(MLX5_RSS_HASH_KEY_LEN ==
+	      (unsigned int)sizeof(rss_hash_default_key),
+	      "wrong RSS default key size.");
 
 /**
  * Check whether Multi-Packet RQ can be enabled for the device.
@@ -1771,7 +1773,7 @@ mlx5_hrxq_new(struct rte_eth_dev *dev,
 		return NULL;
 	}
 	if (!rss_key_len) {
-		rss_key_len = rss_hash_default_key_len;
+		rss_key_len = MLX5_RSS_HASH_KEY_LEN;
 		rss_key = rss_hash_default_key;
 	}
 #ifdef HAVE_IBV_DEVICE_TUNNEL_SUPPORT
@@ -1791,7 +1793,7 @@ mlx5_hrxq_new(struct rte_eth_dev *dev,
 			.rx_hash_conf = (struct ibv_rx_hash_conf){
 				.rx_hash_function = IBV_RX_HASH_FUNC_TOEPLITZ,
 				.rx_hash_key_len = rss_key_len ? rss_key_len :
-						   rss_hash_default_key_len,
+						   MLX5_RSS_HASH_KEY_LEN,
 				.rx_hash_key = rss_key ?
 					       (void *)(uintptr_t)rss_key :
 					       rss_hash_default_key,
@@ -1815,7 +1817,7 @@ mlx5_hrxq_new(struct rte_eth_dev *dev,
 			.rx_hash_conf = (struct ibv_rx_hash_conf){
 				.rx_hash_function = IBV_RX_HASH_FUNC_TOEPLITZ,
 				.rx_hash_key_len = rss_key_len ? rss_key_len :
-						   rss_hash_default_key_len,
+						   MLX5_RSS_HASH_KEY_LEN,
 				.rx_hash_key = rss_key ?
 					       (void *)(uintptr_t)rss_key :
 					       rss_hash_default_key,
@@ -2138,7 +2140,7 @@ mlx5_hrxq_drop_new(struct rte_eth_dev *dev)
 			.rx_hash_conf = (struct ibv_rx_hash_conf){
 				.rx_hash_function =
 					IBV_RX_HASH_FUNC_TOEPLITZ,
-				.rx_hash_key_len = rss_hash_default_key_len,
+				.rx_hash_key_len = MLX5_RSS_HASH_KEY_LEN,
 				.rx_hash_key = rss_hash_default_key,
 				.rx_hash_fields_mask = 0,
 				},
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index 99b769d8a..59e374d8d 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -225,7 +225,6 @@ struct mlx5_txq_ctrl {
 /* mlx5_rxq.c */
 
 extern uint8_t rss_hash_default_key[];
-extern const size_t rss_hash_default_key_len;
 
 int mlx5_check_mprq_support(struct rte_eth_dev *dev);
 int mlx5_rxq_mprq_enabled(struct mlx5_rxq_data *rxq);
