diff --git a/scp.c b/scp.c
index 686328d9..79760db0 100644
--- a/scp.c
+++ b/scp.c
@@ -1185,7 +1185,7 @@ if (dptr->flags & DEV_DEBUG) {
         fprintf (st,  "%-30s\tDisables specific debugging for device %s\n", buf, sim_dname (dptr));
         }
     }
-if ((dptr->modifiers) && (dptr->numunits != 1)) {
+if ((dptr->modifiers) && (dptr->units) && (dptr->numunits != 1)) {
     if (dptr->units->flags & UNIT_DISABLE) {
         fprint_header (st, &found, header);
         sprintf (buf, "set %sn ENABLE", sim_dname (dptr));
@@ -1239,7 +1239,7 @@ if (dptr->flags & DEV_DEBUG) {
     sprintf (buf, "show %s DEBUG", sim_dname (dptr));
     fprintf (st, "%-30s\tDisplays debugging status for device %s\n", buf, sim_dname (dptr));
     }
-if ((dptr->modifiers) && (dptr->numunits != 1)) {
+if ((dptr->modifiers) && (dptr->units) && (dptr->numunits != 1)) {
     for (mptr = dptr->modifiers; mptr->mask != 0; mptr++) {
         if ((!MODMASK(mptr,MTAB_VUN)) && MODMASK(mptr,MTAB_XTD))
             continue;                                           /* skip device only modifiers */