diff --git a/src/bin/pg_upgrade/server.c b/src/bin/pg_upgrade/server.c
index d2391137a8..6f09b99ba6 100644
--- a/src/bin/pg_upgrade/server.c
+++ b/src/bin/pg_upgrade/server.c
@@ -240,6 +240,9 @@ start_postmaster(ClusterInfo *cluster, bool report_and_exit_on_error)
 	 * we only modify the new cluster, so only use it there.  If there is a
 	 * crash, the new cluster has to be recreated anyway.  fsync=off is a big
 	 * win on ext4.
+	 *
+	 * Force vacuum_defer_cleanup_age to 0 on the new cluster, so that
+	 * vacuumdb --freeze actually freezes the tuples.
 	 */
 	snprintf(cmd, sizeof(cmd),
 			 "\"%s/pg_ctl\" -w -l \"%s\" -D \"%s\" -o \"-p %d%s%s %s%s\" start",
@@ -248,7 +251,7 @@ start_postmaster(ClusterInfo *cluster, bool report_and_exit_on_error)
 			  BINARY_UPGRADE_SERVER_FLAG_CAT_VER) ? " -b" :
 			 " -c autovacuum=off -c autovacuum_freeze_max_age=2000000000",
 			 (cluster == &new_cluster) ?
-			 " -c synchronous_commit=off -c fsync=off -c full_page_writes=off" : "",
+			 " -c synchronous_commit=off -c fsync=off -c full_page_writes=off -c vacuum_defer_cleanup_age=0" : "",
 			 cluster->pgopts ? cluster->pgopts : "", socket_string);
 
 	/*