diff --git a/HubConnection.go b/HubConnection.go
index e6c82f8..2943861 100644
--- a/HubConnection.go
+++ b/HubConnection.go
@@ -74,11 +74,15 @@ func (this *HubConnection) userJoined_NameOnly(nick string) {
 }
 
 func (this *HubConnection) userJoined_Full(uinf *UserInfo) {
-	if !this.UserExists(uinf.Nick) {
-		this.userLock.Lock()
-		defer this.userLock.Unlock()
+	// n.b. also called when we get a replacement MyINFO for someone
+	this.userLock.Lock()
+	defer this.userLock.Unlock()
 
-		this.users[uinf.Nick] = *uinf
+	_, userExisted := this.users[uinf.Nick] // don't use UserExists as it would deadlock the mutex
+
+	this.users[uinf.Nick] = *uinf
+
+	if !userExisted {
 		this.processEvent(HubEvent{EventType: EVENT_USER_JOINED, Nick: uinf.Nick})
 	}
 }