diff --git a/src/portable/microchip/pic32mz/dcd_pic32mz.c b/src/portable/microchip/pic32mz/dcd_pic32mz.c
index 7d48f755b..1683d95b4 100644
--- a/src/portable/microchip/pic32mz/dcd_pic32mz.c
+++ b/src/portable/microchip/pic32mz/dcd_pic32mz.c
@@ -530,6 +530,7 @@ static void ep0_handle_rx(void)
 
   transferred = rx_fifo_read(0, xfer->buffer + xfer->transferred);
   xfer->transferred += transferred;
+  TU_ASSERT(xfer->transferred <= xfer->total_len,);
   if (transferred < xfer->max_packet_size || xfer->transferred == xfer->total_len)
   {
     ep0_set_stage(EP0_STAGE_DATA_OUT_COMPLETE);
@@ -560,6 +561,7 @@ static void epn_handle_rx_int(uint8_t epnum)
     transferred = rx_fifo_read(epnum, xfer->buffer + xfer->transferred);
     USB_REGS->EPCSR[epnum].RXCSRL_HOSTbits.RXPKTRDY = 0;
     xfer->transferred += transferred;
+    TU_ASSERT(xfer->transferred <= xfer->total_len,);
     if (transferred < xfer->max_packet_size || xfer->transferred == xfer->total_len)
     {
       xfer_complete(xfer, XFER_RESULT_SUCCESS, true);
@@ -579,6 +581,7 @@ static void epn_handle_tx_int(uint8_t epnum)
   else
   {
     xfer->transferred += xfer->last_packet_size;
+    TU_ASSERT(xfer->transferred <= xfer->total_len,);
     if (xfer->last_packet_size < xfer->max_packet_size || xfer->transferred == xfer->total_len)
     {
       xfer->last_packet_size = 0;