diff --git a/downstream.go b/downstream.go
index d4e9564..8643fcd 100644
--- a/downstream.go
+++ b/downstream.go
@@ -1735,7 +1735,8 @@ func (dc *downstreamConn) handleMessageRegistered(msg *irc.Message) error {
 			}}
 		}
 
-		if dc.user.msgStore == nil {
+		store, ok := dc.user.msgStore.(chatHistoryMessageStore)
+		if !ok {
 			return ircError{&irc.Message{
 				Command: irc.ERR_UNKNOWNCOMMAND,
 				Params:  []string{dc.nick, subcommand, "Unknown command"},
@@ -1775,9 +1776,9 @@ func (dc *downstreamConn) handleMessageRegistered(msg *irc.Message) error {
 		var history []*irc.Message
 		switch subcommand {
 		case "BEFORE":
-			history, err = dc.user.msgStore.LoadBeforeTime(uc.network, entity, timestamp, limit)
+			history, err = store.LoadBeforeTime(uc.network, entity, timestamp, limit)
 		case "AFTER":
-			history, err = dc.user.msgStore.LoadAfterTime(uc.network, entity, timestamp, limit)
+			history, err = store.LoadAfterTime(uc.network, entity, timestamp, limit)
 		default:
 			// TODO: support LATEST, BETWEEN
 			return ircError{&irc.Message{
diff --git a/msgstore.go b/msgstore.go
index 2be4f18..18cd0c9 100644
--- a/msgstore.go
+++ b/msgstore.go
@@ -16,12 +16,19 @@ type messageStore interface {
 	// date. The message ID returned may not refer to a valid message, but can be
 	// used in history queries.
 	LastMsgID(network *network, entity string, t time.Time) (string, error)
-	LoadBeforeTime(network *network, entity string, t time.Time, limit int) ([]*irc.Message, error)
-	LoadAfterTime(network *network, entity string, t time.Time, limit int) ([]*irc.Message, error)
 	LoadLatestID(network *network, entity, id string, limit int) ([]*irc.Message, error)
 	Append(network *network, entity string, msg *irc.Message) (id string, err error)
 }
 
+// chatHistoryMessageStore is a message store that supports chat history
+// operations.
+type chatHistoryMessageStore interface {
+	messageStore
+
+	LoadBeforeTime(network *network, entity string, t time.Time, limit int) ([]*irc.Message, error)
+	LoadAfterTime(network *network, entity string, t time.Time, limit int) ([]*irc.Message, error)
+}
+
 func formatMsgID(netID int64, entity, extra string) string {
 	return fmt.Sprintf("%v %v %v", netID, entity, extra)
 }