diff --git a/bridge/mattermost/mattermost.go b/bridge/mattermost/mattermost.go
index ce4f4c33..e41b19d7 100644
--- a/bridge/mattermost/mattermost.go
+++ b/bridge/mattermost/mattermost.go
@@ -121,6 +121,12 @@ func (b *Bmattermost) Send(msg config.Message) (string, error) {
 		return msg.ID, b.mc.DeleteMessage(msg.ID)
 	}
 
+	// Handle prefix hint for unthreaded messages.
+	if msg.ParentID == "msg-parent-not-found" {
+		msg.ParentID = ""
+		msg.Text = fmt.Sprintf("[thread]: %s", msg.Text)
+	}
+
 	// Upload a file if it exists
 	if msg.Extra != nil {
 		for _, rmsg := range helper.HandleExtra(&msg, b.General) {