diff --git a/drivers/net/mlx5/mlx5_rxtx.c b/drivers/net/mlx5/mlx5_rxtx.c
index 5e58f1afd..7c9d18270 100644
--- a/drivers/net/mlx5/mlx5_rxtx.c
+++ b/drivers/net/mlx5/mlx5_rxtx.c
@@ -357,6 +357,8 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 	/* Start processing. */
 	mlx5_tx_complete(txq);
 	max_elts = (elts_n - (elts_head - txq->elts_tail));
+	/* A CQE slot must always be available. */
+	assert((1u << txq->cqe_n) - (txq->cq_pi - txq->cq_ci));
 	max_wqe = (1u << txq->wqe_n) - (txq->wqe_ci - txq->wqe_pi);
 	if (unlikely(!max_wqe))
 		return 0;
@@ -700,6 +702,9 @@ mlx5_tx_burst(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 		/* Save elts_head in unused "immediate" field of WQE. */
 		last_wqe->ctrl3 = txq->elts_head;
 		txq->elts_comp = 0;
+#ifndef NDEBUG
+		++txq->cq_pi;
+#endif
 	} else {
 		txq->elts_comp = comp;
 	}
@@ -818,6 +823,8 @@ mlx5_tx_burst_mpw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 	/* Start processing. */
 	mlx5_tx_complete(txq);
 	max_elts = (elts_n - (elts_head - txq->elts_tail));
+	/* A CQE slot must always be available. */
+	assert((1u << txq->cqe_n) - (txq->cq_pi - txq->cq_ci));
 	max_wqe = (1u << txq->wqe_n) - (txq->wqe_ci - txq->wqe_pi);
 	if (unlikely(!max_wqe))
 		return 0;
@@ -911,6 +918,9 @@ mlx5_tx_burst_mpw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 		/* Save elts_head in unused "immediate" field of WQE. */
 		wqe->ctrl[3] = elts_head;
 		txq->elts_comp = 0;
+#ifndef NDEBUG
+		++txq->cq_pi;
+#endif
 	} else {
 		txq->elts_comp = comp;
 	}
@@ -1042,6 +1052,8 @@ mlx5_tx_burst_mpw_inline(void *dpdk_txq, struct rte_mbuf **pkts,
 	/* Start processing. */
 	mlx5_tx_complete(txq);
 	max_elts = (elts_n - (elts_head - txq->elts_tail));
+	/* A CQE slot must always be available. */
+	assert((1u << txq->cqe_n) - (txq->cq_pi - txq->cq_ci));
 	do {
 		struct rte_mbuf *buf = *(pkts++);
 		uintptr_t addr;
@@ -1203,6 +1215,9 @@ mlx5_tx_burst_mpw_inline(void *dpdk_txq, struct rte_mbuf **pkts,
 		/* Save elts_head in unused "immediate" field of WQE. */
 		wqe->ctrl[3] = elts_head;
 		txq->elts_comp = 0;
+#ifndef NDEBUG
+		++txq->cq_pi;
+#endif
 	} else {
 		txq->elts_comp = comp;
 	}
@@ -1549,7 +1564,9 @@ mlx5_tx_burst_empw(void *dpdk_txq, struct rte_mbuf **pkts, uint16_t pkts_n)
 		wqe->ctrl[3] = elts_head;
 		txq->elts_comp = 0;
 		txq->mpw_comp = txq->wqe_ci;
-		txq->cq_pi++;
+#ifndef NDEBUG
+		++txq->cq_pi;
+#endif
 	} else {
 		txq->elts_comp += j;
 	}
diff --git a/drivers/net/mlx5/mlx5_rxtx.h b/drivers/net/mlx5/mlx5_rxtx.h
index b783ca203..c072169f2 100644
--- a/drivers/net/mlx5/mlx5_rxtx.h
+++ b/drivers/net/mlx5/mlx5_rxtx.h
@@ -185,7 +185,9 @@ struct mlx5_txq_data {
 	uint16_t elts_comp; /* Counter since last completion request. */
 	uint16_t mpw_comp; /* WQ index since last completion request. */
 	uint16_t cq_ci; /* Consumer index for completion queue. */
+#ifndef NDEBUG
 	uint16_t cq_pi; /* Producer index for completion queue. */
+#endif
 	uint16_t wqe_ci; /* Consumer index for work queue. */
 	uint16_t wqe_pi; /* Producer index for work queue. */
 	uint16_t elts_n:4; /* (*elts)[] length (in log2). */
diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
index 77ce0c3e0..661fbf11c 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_neon.h
@@ -135,6 +135,8 @@ txq_scatter_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts,
 
 	assert(elts_n > pkts_n);
 	mlx5_tx_complete(txq);
+	/* A CQE slot must always be available. */
+	assert((1u << txq->cqe_n) - (txq->cq_pi - txq->cq_ci));
 	if (unlikely(!pkts_n))
 		return 0;
 	for (n = 0; n < pkts_n; ++n) {
@@ -205,7 +207,9 @@ txq_scatter_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts,
 		wqe->ctrl[2] = rte_cpu_to_be_32(8);
 		wqe->ctrl[3] = txq->elts_head;
 		txq->elts_comp = 0;
+#ifndef NDEBUG
 		++txq->cq_pi;
+#endif
 	}
 #ifdef MLX5_PMD_SOFT_COUNTERS
 	txq->stats.opackets += n;
@@ -269,6 +273,8 @@ txq_burst_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts, uint16_t pkts_n,
 	assert(elts_n > pkts_n);
 	mlx5_tx_complete(txq);
 	max_elts = (elts_n - (elts_head - txq->elts_tail));
+	/* A CQE slot must always be available. */
+	assert((1u << txq->cqe_n) - (txq->cq_pi - txq->cq_ci));
 	max_wqe = (1u << txq->wqe_n) - (txq->wqe_ci - txq->wqe_pi);
 	pkts_n = RTE_MIN((unsigned int)RTE_MIN(pkts_n, max_wqe), max_elts);
 	if (unlikely(!pkts_n))
@@ -306,7 +312,9 @@ txq_burst_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts, uint16_t pkts_n,
 	} else {
 		/* Request a completion. */
 		txq->elts_comp = 0;
+#ifndef NDEBUG
 		++txq->cq_pi;
+#endif
 		comp_req = 8;
 	}
 	/* Fill CTRL in the header. */
diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
index f25681184..2b0e62861 100644
--- a/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_sse.h
@@ -135,6 +135,8 @@ txq_scatter_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts,
 
 	assert(elts_n > pkts_n);
 	mlx5_tx_complete(txq);
+	/* A CQE slot must always be available. */
+	assert((1u << txq->cqe_n) - (txq->cq_pi - txq->cq_ci));
 	if (unlikely(!pkts_n))
 		return 0;
 	for (n = 0; n < pkts_n; ++n) {
@@ -206,7 +208,9 @@ txq_scatter_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts,
 		wqe->ctrl[2] = rte_cpu_to_be_32(8);
 		wqe->ctrl[3] = txq->elts_head;
 		txq->elts_comp = 0;
+#ifndef NDEBUG
 		++txq->cq_pi;
+#endif
 	}
 #ifdef MLX5_PMD_SOFT_COUNTERS
 	txq->stats.opackets += n;
@@ -268,6 +272,8 @@ txq_burst_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts, uint16_t pkts_n,
 	assert(elts_n > pkts_n);
 	mlx5_tx_complete(txq);
 	max_elts = (elts_n - (elts_head - txq->elts_tail));
+	/* A CQE slot must always be available. */
+	assert((1u << txq->cqe_n) - (txq->cq_pi - txq->cq_ci));
 	max_wqe = (1u << txq->wqe_n) - (txq->wqe_ci - txq->wqe_pi);
 	pkts_n = RTE_MIN((unsigned int)RTE_MIN(pkts_n, max_wqe), max_elts);
 	assert(pkts_n <= MLX5_DSEG_MAX - nb_dword_in_hdr);
@@ -307,7 +313,9 @@ txq_burst_v(struct mlx5_txq_data *txq, struct rte_mbuf **pkts, uint16_t pkts_n,
 	} else {
 		/* Request a completion. */
 		txq->elts_comp = 0;
+#ifndef NDEBUG
 		++txq->cq_pi;
+#endif
 		comp_req = 8;
 	}
 	/* Fill CTRL in the header. */
diff --git a/drivers/net/mlx5/mlx5_txq.c b/drivers/net/mlx5/mlx5_txq.c
index a786a6b63..89b16fda2 100644
--- a/drivers/net/mlx5/mlx5_txq.c
+++ b/drivers/net/mlx5/mlx5_txq.c
@@ -418,7 +418,9 @@ mlx5_priv_txq_ibv_new(struct priv *priv, uint16_t idx)
 		(volatile struct mlx5_cqe (*)[])
 		(uintptr_t)cq_info.buf;
 	txq_data->cq_ci = 0;
+#ifndef NDEBUG
 	txq_data->cq_pi = 0;
+#endif
 	txq_data->wqe_ci = 0;
 	txq_data->wqe_pi = 0;
 	txq_ibv->qp = tmpl.qp;
