diff --git a/mps/code/zonedcbs.c b/mps/code/zonedcbs.c
index 208fc08e5ac..4ecf8134868 100644
--- a/mps/code/zonedcbs.c
+++ b/mps/code/zonedcbs.c
@@ -127,6 +127,8 @@ void ZonedCBSFinish(ZonedCBS zcbs)
 
 Res ZonedCBSInsert(Range rangeReturn, ZonedCBS zcbs, Range range)
 {
+  ZoneSet zs;
+
   AVERT(ZonedCBS, zcbs);
 
   /* TODO: Consider moving empty zone stripes back to freeCBS. At the
@@ -136,6 +138,13 @@ Res ZonedCBSInsert(Range rangeReturn, ZonedCBS zcbs, Range range)
      eagerly in any case, but lazily if we're unable to find address
      space, even though that reduces first-fit. */
 
+  zs = ZoneSetOfRange(zcbs->arena, RangeBase(range), RangeLimit(range));
+  if (ZoneSetIsSingle(zs)) {
+    Index zone = AddrZone(zcbs->arena, RangeBase(range));
+    CBS zoneCBS = ZonedCBSZoneCBS(zcbs, zone);
+    return CBSInsert(rangeReturn, zoneCBS, range);
+  }
+
   return CBSInsert(rangeReturn, ZonedCBSFreeCBS(zcbs), range);
 }