diff --git a/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go b/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go
index d522cde9bcb..9bfa3a0a778 100644
--- a/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go
+++ b/staging/src/k8s.io/apiserver/pkg/server/options/etcd.go
@@ -120,7 +120,8 @@ func (s *EtcdOptions) AddFlags(fs *pflag.FlagSet) {
 	fs.StringSliceVar(&s.WatchCacheSizes, "watch-cache-sizes", s.WatchCacheSizes, ""+
 		"List of watch cache sizes for every resource (pods, nodes, etc.), comma separated. "+
 		"The individual override format: resource#size, where size is a number. It takes effect "+
-		"when watch-cache is enabled.")
+		"when watch-cache is enabled. Some resources (replicationcontrollers, endpoints, nodes, pods, services, apiservices) "+
+		"have system defaults set by heuristics, others default to default-watch-cache-size")
 
 	fs.StringVar(&s.StorageConfig.Type, "storage-backend", s.StorageConfig.Type,
 		"The storage backend for persistence. Options: 'etcd3' (default), 'etcd2'.")