diff --git a/src/bot.ts b/src/bot.ts
index 46820af..e83a413 100644
--- a/src/bot.ts
+++ b/src/bot.ts
@@ -32,8 +32,8 @@ export class ChannelBot {
     process.once('SIGINT', () => this.bot.stop('SIGINT'));
     process.once('SIGTERM', () => this.bot.stop('SIGTERM'));
 
-    this.bot.on('chat_member', (ctx) => this.handleChatMemberUpdate(ctx));
-
+    this.bot.on('chat_member', this.handleChatMemberUpdate.bind(this));
+    
     this.bot.launch(
       {
         allowedUpdates: [