diff --git a/drivers/ethernet/eth_sam_gmac_priv.h b/drivers/ethernet/eth_sam_gmac_priv.h
index 4eee362d126..ae6453c0fda 100644
--- a/drivers/ethernet/eth_sam_gmac_priv.h
+++ b/drivers/ethernet/eth_sam_gmac_priv.h
@@ -30,8 +30,11 @@
 
 /** RX descriptors count for main queue */
 #define MAIN_QUEUE_RX_DESC_COUNT CONFIG_ETH_SAM_GMAC_BUF_RX_COUNT
-/** TX descriptors count for main queue */
-#define MAIN_QUEUE_TX_DESC_COUNT (CONFIG_NET_BUF_TX_COUNT + 1)
+/** TX descriptors count for main queue. They should be able to store a full
+ ** packet, that might use either the TX or the RX buffers.
+ */
+#define MAIN_QUEUE_TX_DESC_COUNT (max(CONFIG_NET_BUF_RX_COUNT, \
+				      CONFIG_NET_BUF_TX_COUNT) + 1)
 
 /** RX/TX descriptors count for priority queues */
 #if GMAC_PRIORITY_QUEUE_NO == 2