diff --git a/NTFConfig.go b/NTFConfig.go
index c0237eb..7524bc8 100644
--- a/NTFConfig.go
+++ b/NTFConfig.go
@@ -8,11 +8,12 @@ import (
 // NTFConfig keeps track of setup properties as well as runtime state.
 // FIXME separate compile-time and run-time properties into separate files
 type NTFConfig struct {
-	HubAddr        string
-	HubDescription string
-	HubSecNick     string // Nickname of Hub-Security to exclude (e.g. "PtokaX")
-	BotAPIKey      string
-	GroupChatID    int64
+	HubAddr         string
+	HubDescription  string
+	HubSecNick      string // Nickname of Hub-Security to exclude (e.g. "PtokaX")
+	HubNickMinChars int
+	BotAPIKey       string
+	GroupChatID     int64
 
 	// Map of telegram user IDs to NMDC nicks
 	KnownUsers map[int64]string
diff --git a/NTFServer.go b/NTFServer.go
index ea06029..3d4e74c 100644
--- a/NTFServer.go
+++ b/NTFServer.go
@@ -544,6 +544,12 @@ func (this *NTFServer) HandleDirectMessage(update telegram.Update) error {
 
 	} else if strings.HasPrefix(msg, "/join ") {
 		requestedHubNick := msg[6:]
+
+		// Minimum nick lengths
+		if len(requestedHubNick) < this.config.HubNickMinChars {
+			return respond(fmt.Sprintf("Upstream nickname '%s' should be at least %d characters long", requestedHubNick, this.config.HubNickMinChars))
+		}
+
 		err := this.registerUser(userID, requestedHubNick)
 		if err != nil {
 			log.Printf("Failed to register user: %s", err.Error())