--- b/sys/vm/uma_core.c	
+++ b/sys/vm/uma_core.c	
@@ -362,13 +362,32 @@ bucket_init(void)
  * to allocate the bucket.
  */
 static struct uma_bucket_zone *
-bucket_zone_lookup(int entries)
+bucket_zone_lookup(uma_zone_t zone, int entries)
 {
 	struct uma_bucket_zone *ubz;
+	uma_keg_t keg;
 
-	for (ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++)
-		if (ubz->ubz_entries >= entries)
-			return (ubz);
+	for (ubz = &bucket_zones[0]; ubz->ubz_entries != 0; ubz++) {
+		if (ubz->ubz_entries < entries)
+			continue;
+#ifdef DEBUG_MEMGUARD
+		if (zone == ubz->ubz_zone) {
+			if ((ubz + 1)->ubz_entries != 0)
+				continue;
+			return (memguard_cmp_zone((ubz - 1)->ubz_zone) ?
+			    ubz - 2 : ubz - 1);
+		}
+		if (zone != NULL && memguard_cmp_zone(ubz->ubz_zone) &&
+		    (keg = zone_first_keg(zone)) != NULL &&
+		    (keg->uk_flags & (UMA_ZONE_VM | UMA_ZFLAG_BUCKET)) != 0) {
+			if ((ubz + 1)->ubz_entries == 0)
+				return (zone == (ubz - 1)->ubz_zone ?
+				    ubz - 2 : ubz - 1);
+			continue;
+		}
+#endif
+		return (ubz);
+	}
 	ubz--;
 	return (ubz);
 }
@@ -422,7 +441,7 @@ bucket_alloc(uma_zone_t zone, void *udata, int flags)
 	}
 	if ((uintptr_t)udata & UMA_ZFLAG_CACHEONLY)
 		flags |= M_NOVM;
-	ubz = bucket_zone_lookup(zone->uz_count);
+	ubz = bucket_zone_lookup(zone, zone->uz_count);
 	if (ubz->ubz_zone == zone && (ubz + 1)->ubz_entries != 0)
 		ubz++;
 	bucket = uma_zalloc_arg(ubz->ubz_zone, udata, flags);
@@ -446,7 +465,7 @@ bucket_free(uma_zone_t zone, uma_bucket_t bucket, void *udata)
 	    ("bucket_free: Freeing a non free bucket."));
 	if ((zone->uz_flags & UMA_ZFLAG_BUCKET) == 0)
 		udata = (void *)(uintptr_t)zone->uz_flags;
-	ubz = bucket_zone_lookup(bucket->ub_entries);
+	ubz = bucket_zone_lookup(NULL, bucket->ub_entries);
 	uma_zfree_arg(ubz->ubz_zone, bucket, udata);
 }