diff --git a/os/hal/ports/SAMA/LLD/MACv1/hal_mac_lld.c b/os/hal/ports/SAMA/LLD/MACv1/hal_mac_lld.c
index 56b9939ad..0be3c7d91 100644
--- a/os/hal/ports/SAMA/LLD/MACv1/hal_mac_lld.c
+++ b/os/hal/ports/SAMA/LLD/MACv1/hal_mac_lld.c
@@ -539,7 +539,7 @@ void mac_lld_release_transmit_descriptor(MACTransmitDescriptor *tdp) {
   osalSysLock();
 
   /* Unlocks the descriptor and returns it to the DMA engine.*/
-  tdp->physdesc->tdes1 = SAMA_TDES1_LAST_BUFF | (SAMA_TDES1_LENGTH_BUFF & BUFFER_SIZE);
+  tdp->physdesc->tdes1 &= ~(SAMA_TDES1_LOCKED | SAMA_TDES1_USED);
 
   /* Wait for the write to tdes1 to go through before resuming the DMA.*/
   __DSB();
@@ -728,6 +728,9 @@ size_t mac_lld_write_transmit_descriptor(MACTransmitDescriptor *tdp,
   if (size > tdp->size - tdp->offset)
     size = tdp->size - tdp->offset;
 
+  /* Configure lentgh of buffer */
+  tdp->physdesc->tdes1 |= (SAMA_TDES1_LENGTH_BUFF & size);
+
   if (size > 0) {
     memcpy((uint8_t *)(tdp->physdesc->tdes0) + tdp->offset, buf, size);
     tdp->offset += size;