diff --git a/C/compiler.c b/C/compiler.c
index 97ca36c95..9d6999ba9 100644
--- a/C/compiler.c
+++ b/C/compiler.c
@@ -171,6 +171,7 @@ static char SccsId[] = "%W% %G%";
 #include "Yap.h"
 #include "compile.h"
 #include "clause.h"
+#include "alloc.h"
 #include "yapio.h"
 #if HAVE_STRING_H
 #include <string.h>
@@ -2698,7 +2699,7 @@ checkreg(Int arg, Int rn, compiler_vm_op ic, int var_arg, compiler_struct *cglob
 static CELL
 copy_live_temps_bmap(int max, compiler_struct *cglobs)
 {
-  unsigned int size = (max|7)/8+1;
+  unsigned int size = AdjustSize((max|7)/8+1);
   int i;
   CELL *dest = Yap_emit_extra_size(mark_live_regs_op, max, size, &cglobs->cint);
   CELL *ptr=dest;
diff --git a/C/heapgc.c b/C/heapgc.c
index a6267079b..53b939497 100644
--- a/C/heapgc.c
+++ b/C/heapgc.c
@@ -1700,7 +1700,8 @@ mark_trail(tr_fr_ptr trail_ptr, tr_fr_ptr trail_base, CELL *gc_H, choiceptr gc_B
     } else if (IsPairTerm(trail_cell)) {
       /* can safely ignore this */
       CELL *cptr = RepPair(trail_cell);
-      if (IsAttVar(cptr)) {
+      if (IN_BETWEEN(H0,cptr,H) &&
+	  IsAttVar(cptr)) {
 	TrailTerm(trail_base) = (CELL)cptr;
 	mark_external_reference(&TrailTerm(trail_base));
 	TrailTerm(trail_base) = trail_cell;