diff --git a/PDP11/pdp11_xq.c b/PDP11/pdp11_xq.c
index 7a1011b9..7bab1e08 100644
--- a/PDP11/pdp11_xq.c
+++ b/PDP11/pdp11_xq.c
@@ -1162,7 +1162,7 @@ t_stat xq_process_rbdl(CTLR* xq)
          the physical layer (sim_ether) won't deliver any short packets 
          via eth_read, so the only short packets which get here are loopback
          packets sent by the host diagnostics (OR short setup packets) */
-      if ((item->type == 2) && (rbl < ETH_MIN_PACKET)) {
+      if ((item->type == ETH_ITM_NORMAL) && (rbl < ETH_MIN_PACKET)) {
         xq->var->stats.runt += 1;
         sim_debug(DBG_WRN, xq->dev, "Runt detected, size = %d\n", rbl);
         /* pad runts with zeros up to minimum size - this allows "legal" (size - 60)
@@ -1172,7 +1172,7 @@ t_stat xq_process_rbdl(CTLR* xq)
       };
 
       /* adjust oversized non-loopback packets */
-      if ((item->type != 1) && (rbl > ETH_FRAME_SIZE)) {
+      if ((item->type != ETH_ITM_LOOPBACK) && (rbl > ETH_FRAME_SIZE)) {
         xq->var->stats.giant += 1;
         sim_debug(DBG_WRN, xq->dev, "Giant detected, size=%d\n", rbl);
         /* trim giants down to maximum size - no documentation on how to handle the data loss */
@@ -1197,7 +1197,7 @@ t_stat xq_process_rbdl(CTLR* xq)
 
     xq->var->rbdl_buf[4] = 0;
     switch (item->type) {
-      case 0: /* setup packet */
+      case ETH_ITM_SETUP: /* setup packet */
         xq->var->stats.setup += 1;
         xq->var->rbdl_buf[4] = 0x2700;      /* set esetup and RBL 10:8 */
         if (xq->var->type == XQ_T_DEQNA) {  /* Strange DEQNA behavior */
@@ -1209,7 +1209,7 @@ t_stat xq_process_rbdl(CTLR* xq)
           }
         }
         break;
-      case 1: /* loopback packet */
+      case ETH_ITM_LOOPBACK: /* loopback packet */
         xq->var->stats.loop += 1;
         xq->var->rbdl_buf[4] = XQ_RST_LASTNOERR;
         if (xq->var->type == XQ_T_DEQNA)
@@ -1220,7 +1220,7 @@ t_stat xq_process_rbdl(CTLR* xq)
         if (xq->var->csr & XQ_CSR_EL)
             xq->var->rbdl_buf[4] |= XQ_RST_ESETUP;/* loopback flag */
         break;
-      case 2: /* normal packet */
+      case ETH_ITM_NORMAL: /* normal packet */
         rbl -= 60;    /* keeps max packet size in 11 bits */
         xq->var->rbdl_buf[4] = (rbl & 0x0700); /* high bits of rbl */
         xq->var->rbdl_buf[4] |= 0x00f8;        /* set reserved bits to 1 */
@@ -1236,8 +1236,8 @@ t_stat xq_process_rbdl(CTLR* xq)
       xq->var->ReadQ.loss = 0;                  /* reset loss counter */
       }
     if (((~xq->var->csr & XQ_CSR_EL) &&
-         ((rbl + ((item->type == 2) ? 60 : 0)) > ETH_MAX_PACKET)) ||
-        ((xq->var->csr & XQ_CSR_EL) && (item->type == 1) && 
+         ((rbl + ((item->type == ETH_ITM_NORMAL) ? 60 : 0)) > ETH_MAX_PACKET)) ||
+        ((xq->var->csr & XQ_CSR_EL) && (item->type == ETH_ITM_LOOPBACK) && 
          (rbl >= XQ_LONG_PACKET)))
       xq->var->rbdl_buf[4] |= XQ_RST_LASTERR;   /* set Error bit (LONG) */
 
@@ -1245,7 +1245,8 @@ t_stat xq_process_rbdl(CTLR* xq)
     wstatus = Map_WriteW(xq->var->rbdl_ba + 8, 4, &xq->var->rbdl_buf[4]);
     if (wstatus) return xq_nxm_error(xq);
 
-    sim_debug(DBG_TRC, xq->dev, "xq_process_rdbl(bd=0x%X, addr=0x%X, size=0x%X, len=0x%X, st1=0x%04X, st2=0x%04X)\n", xq->var->rbdl_ba, address, b_length, rbl + ((item->type == 2) ? 60 : 0), xq->var->rbdl_buf[4], xq->var->rbdl_buf[5]);
+    sim_debug(DBG_TRC, xq->dev, "xq_process_rdbl(bd=0x%X, addr=0x%X, size=0x%X, len=0x%X, st1=0x%04X, st2=0x%04X)\n", 
+        xq->var->rbdl_ba, address, b_length, rbl + ((item->type == ETH_ITM_NORMAL) ? 60 : 0), xq->var->rbdl_buf[4], xq->var->rbdl_buf[5]);
 
     /* remove packet from queue */
     if (item->packet.used >= item->packet.len) {
@@ -1748,7 +1749,7 @@ t_stat xq_process_turbo_rbdl(CTLR* xq)
       rbuf = &item->packet.msg[used];
     } else {
       /* adjust non loopback runt packets */
-      if ((item->type != 1) && (rbl < ETH_MIN_PACKET)) {
+      if ((item->type != ETH_ITM_LOOPBACK) && (rbl < ETH_MIN_PACKET)) {
         xq->var->stats.runt += 1;
         sim_debug(DBG_WRN, xq->dev, "Runt detected, size = %d\n", rbl);
         /* pad runts with zeros up to minimum size - this allows "legal" (size - 60)
@@ -1758,7 +1759,7 @@ t_stat xq_process_turbo_rbdl(CTLR* xq)
       };
 
       /* adjust oversized non-loopback packets */
-      if ((item->type != 1) && (rbl > ETH_FRAME_SIZE)) {
+      if ((item->type != ETH_ITM_LOOPBACK) && (rbl > ETH_FRAME_SIZE)) {
         xq->var->stats.giant += 1;
         sim_debug(DBG_WRN, xq->dev, "Giant detected, size=%d\n", rbl);
         /* trim giants down to maximum size - no documentation on how to handle the data loss */
@@ -2062,8 +2063,9 @@ void xq_read_callback(CTLR* xq, int status)
   if (DBG_PCK & xq->dev->dctrl)
     eth_packet_trace_ex(xq->var->etherface, xq->var->read_buffer.msg, xq->var->read_buffer.len, "xq-recvd", DBG_DAT & xq->dev->dctrl, DBG_PCK);
 
-  if ((xq->var->csr & XQ_CSR_RE) || (xq->var->mode == XQ_T_DELQA_PLUS)) { /* receiver enabled */
+  xq->var->read_buffer.used = 0;  /* none processed yet */
 
+  if ((xq->var->csr & XQ_CSR_RE) || (xq->var->mode == XQ_T_DELQA_PLUS)) { /* receiver enabled */
     /* process any packets locally that can be */
     t_stat status = xq_process_local (xq, &xq->var->read_buffer);
 
diff --git a/PDP11/pdp11_xu.c b/PDP11/pdp11_xu.c
index ad5a7e40..2a6a4d89 100644
--- a/PDP11/pdp11_xu.c
+++ b/PDP11/pdp11_xu.c
@@ -619,12 +619,14 @@ void xu_read_callback(CTLR* xu, int status)
   if (DBG_PCK & xu->dev->dctrl)
       eth_packet_trace_ex(xu->var->etherface, xu->var->read_buffer.msg, xu->var->read_buffer.len, "xu-recvd", DBG_DAT & xu->dev->dctrl, DBG_PCK);
 
+  xu->var->read_buffer.used = 0;  /* none processed yet */
+
   /* process any packets locally that can be */
   status = xu_process_local (xu, &xu->var->read_buffer);
 
   /* add packet to read queue */
   if (status != SCPE_OK)
-    ethq_insert(&xu->var->ReadQ, 2, &xu->var->read_buffer, 0);
+    ethq_insert(&xu->var->ReadQ, ETH_ITM_NORMAL, &xu->var->read_buffer, 0);
 }
 
 void xua_read_callback(int status)
@@ -1425,7 +1427,7 @@ void xu_process_transmit(CTLR* xu)
       /* are we in internal loopback mode ? */
       if ((xu->var->mode & MODE_LOOP) && (xu->var->mode & MODE_INTL)) {
         /* just put packet in  receive buffer */
-        ethq_insert (&xu->var->ReadQ, 1, &xu->var->write_buffer, 0);
+        ethq_insert (&xu->var->ReadQ, ETH_ITM_LOOPBACK, &xu->var->write_buffer, 0);
       } else {
         /* transmit packet synchronously - write callback sets status */
         wstatus = eth_write(xu->var->etherface, &xu->var->write_buffer, xu->var->wcallback);
diff --git a/sim_ether.c b/sim_ether.c
index ba667194..059f7ac3 100644
--- a/sim_ether.c
+++ b/sim_ether.c
@@ -3168,7 +3168,7 @@ if (bpf_used ? to_me : (to_me && !from_me)) {
     eth_packet_trace (dev, data, len, "rcvqd");
 
     pthread_mutex_lock (&dev->lock);
-    ethq_insert_data(&dev->read_queue, 2, data, 0, len, crc_len, crc_data, 0);
+    ethq_insert_data(&dev->read_queue, ETH_ITM_NORMAL, data, 0, len, crc_len, crc_data, 0);
     ++dev->packets_received;
     pthread_mutex_unlock (&dev->lock);
     free(moved_data);
diff --git a/sim_ether.h b/sim_ether.h
index 15a06b9a..875651d3 100644
--- a/sim_ether.h
+++ b/sim_ether.h
@@ -206,6 +206,9 @@ struct eth_packet {
 
 struct eth_item {
   int                 type;                             /* receive (0=setup, 1=loopback, 2=normal) */
+#define ETH_ITM_SETUP    0
+#define ETH_ITM_LOOPBACK 1
+#define ETH_ITM_NORMAL   2
   struct eth_packet   packet;
 };