diff --git a/H/amiops.h b/H/amiops.h
index b2968f037..bd6d25c09 100644
--- a/H/amiops.h
+++ b/H/amiops.h
@@ -436,6 +436,38 @@ reset_trail(tr_fr_ptr TR0) {
   }
 }
 
+inline EXTERN void
+reset_attvars(CELL *dvarsmin, CELL *dvarsmax) {
+  if (dvarsmin) {
+    dvarsmin += 1;
+    do {
+      CELL *newv;
+      newv = CellPtr(*dvarsmin);
+      RESET_VARIABLE(dvarsmin+1);
+      if (IsUnboundVar(dvarsmin))
+	break;
+      RESET_VARIABLE(dvarsmin);
+      dvarsmin = newv;
+    } while (TRUE);
+  }
+}
+
+inline EXTERN void
+close_attvar_chain(CELL *dvarsmin, CELL *dvarsmax) {
+  if (dvarsmin) {
+    dvarsmin += 1;
+    do {
+      CELL *newv;
+      Bind(dvarsmin+1, dvarsmin[1]);
+      if (IsUnboundVar(dvarsmin))
+	break;
+      newv = CellPtr(*dvarsmin);
+      RESET_VARIABLE(dvarsmin);
+      dvarsmin = newv;
+    } while (TRUE);
+  }
+}
+
 EXTERN inline
 Int Yap_unify(Term t0, Term t1)
 {
diff --git a/packages/chr b/packages/chr
index 99090acf4..91ad6583a 160000
--- a/packages/chr
+++ b/packages/chr
@@ -1 +1 @@
-Subproject commit 99090acf47044ad4a6dc78da634668bdc2bae485
+Subproject commit 91ad6583a1387ad6c645c46f258fd671d92fe9fb