diff --git a/C/grow.c b/C/grow.c
index 65fb73720..df1cf62e1 100644
--- a/C/grow.c
+++ b/C/grow.c
@@ -1518,7 +1518,7 @@ Yap_growtrail_in_parser(tr_fr_ptr *old_trp, TokEntry **tksp, VarEntry **vep)
 CELL **
 Yap_shift_visit(CELL **to_visit, CELL ***to_visit_maxp)
 {
-#if USE_SYSTEM_MALLOC || USE_DL_MALLOC
+#if USE_SYSTEM_MALLOC
   CELL **to_visit_max = *to_visit_maxp;
   Int sz1 = (CELL)to_visit_max-(CELL)to_visit;
   Int sz0 = AuxTop - (ADDR)to_visit_maxp, sz, dsz;
diff --git a/C/utilpreds.c b/C/utilpreds.c
index f518ca941..e555c90e1 100644
--- a/C/utilpreds.c
+++ b/C/utilpreds.c
@@ -521,6 +521,9 @@ static Term vars_in_complex_term(register CELL *pt0, register CELL *pt0_end, Ter
   vars_in_term_nvar:
     {
       if (IsPairTerm(d0)) {
+	if (to_visit + 1024 >= (CELL **)AuxSp) {
+	  goto aux_overflow;
+	}
 #ifdef RATIONAL_TREES
 	to_visit[0] = pt0;
 	to_visit[1] = pt0_end;
@@ -547,6 +550,9 @@ static Term vars_in_complex_term(register CELL *pt0, register CELL *pt0_end, Ter
 	  continue;
 	}
 	/* store the terms to visit */
+	if (to_visit + 1024 >= (CELL **)AuxSp) {
+	  goto aux_overflow;
+	}
 #ifdef RATIONAL_TREES
 	to_visit[0] = pt0;
 	to_visit[1] = pt0_end;
@@ -633,6 +639,21 @@ static Term vars_in_complex_term(register CELL *pt0, register CELL *pt0_end, Ter
   H = InitialH;
   return 0L;
   
+ aux_overflow:
+  Yap_Error_Size = (to_visit-to_visit0)*sizeof(CELL **);
+#ifdef RATIONAL_TREES
+  while (to_visit > to_visit0) {
+    to_visit -= 3;
+    pt0 = to_visit[0];
+    *pt0 = (CELL)to_visit[2];
+  }
+#endif
+  Yap_Error_TYPE = OUT_OF_AUXSPACE_ERROR;
+  clean_tr(TR0);
+  Yap_ReleasePreAllocCodeSpace((ADDR)to_visit0);
+  H = InitialH;
+  return 0L;
+  
  global_overflow:
 #ifdef RATIONAL_TREES
   while (to_visit > to_visit0) {
@@ -663,6 +684,13 @@ expand_vts(void)
     if (!Yap_growtrail(expand, FALSE)) {
       return FALSE;
     }
+  } else if (yap_errno == OUT_OF_AUXSPACE_ERROR) {
+    /* Aux space overflow */
+    if (expand > 4*1024*1024)
+      expand = 4*1024*1024;
+    if (!Yap_ExpandPreAllocCodeSpace(expand, NULL)) {
+      return FALSE;
+    }
   } else {
     if (!Yap_gcl(expand, 3, ENV, P)) {
       Yap_Error(OUT_OF_STACK_ERROR, TermNil, "in term_variables");
diff --git a/changes-5.1.html b/changes-5.1.html
index e19369632..b500f552a 100644
--- a/changes-5.1.html
+++ b/changes-5.1.html
@@ -17,6 +17,10 @@
 
 <h2>Yap-5.1.3:</h2>
 <ul>
+<li> FIXED: Yap_shift_visit assumed we were using AUX DL_MALLOC (obs
+  from Bernd Gutmann).</li>
+<li> FIXED: auxiliary stack overflow in term_vars (obs from Bernd
+  Gutmann).</li>
 <li> FIXED: trail overflow while copying huge terms (obs from Bernd
   Gutmann).</li>
 <li> NEW: compilation_mode option for load_files (request from