diff --git a/server/methods.ts b/server/methods.ts
index 43445c4..d8cf583 100644
--- a/server/methods.ts
+++ b/server/methods.ts
@@ -23,6 +23,9 @@ Meteor.methods({
   },
 
   addMessage(type: MessageType, chatId: string, content: string) {
+    if (!this.userId) throw new Meteor.Error('unauthorized',
+      'User must be logged-in to create a new chat');
+
     check(type, Match.OneOf(String, [ MessageType.TEXT ]));
     check(chatId, nonEmptyString);
     check(content, nonEmptyString);
@@ -37,6 +40,7 @@ Meteor.methods({
     return {
       messageId: Messages.collection.insert({
         chatId: chatId,
+        senderId: this.userId,
         content: content,
         createdAt: new Date(),
         type: type