diff --git a/disco/gateway/client.py b/disco/gateway/client.py
index b8ceecc..a7b5d36 100644
--- a/disco/gateway/client.py
+++ b/disco/gateway/client.py
@@ -68,7 +68,7 @@ class GatewayClient(LoggingClass):
 
         # Heartbeat
         self._heartbeat_task = None
-        self.heartbeat_acknowledged = True
+        self._heartbeat_acknowledged = True
 
     def send(self, op, data):
         self.limiter.check()
@@ -84,14 +84,14 @@ class GatewayClient(LoggingClass):
 
     def heartbeat_task(self, interval):
         while True:
-            if not self.heartbeat_acknowledged:
+            if not self._heartbeat_acknowledged:
                 self.log.warning('Received HEARTBEAT without HEARTBEAT_ACK, forcing a fresh reconnect')
-                self.heartbeat_acknowledged = True
-                self.ws.close()
+                self._heartbeat_acknowledged = True
+                self.ws.close(status=4000)
                 return
 
             self._send(OPCode.HEARTBEAT, self.seq)
-            self.heartbeat_acknowledged = False
+            self._heartbeat_acknowledged = False
             gevent.sleep(interval / 1000)
 
     def handle_dispatch(self, packet):
@@ -106,7 +106,7 @@ class GatewayClient(LoggingClass):
 
     def handle_heartbeat_acknowledge(self, _):
         self.log.debug('Received HEARTBEAT_ACK')
-        self.heartbeat_acknowledged = True
+        self._heartbeat_acknowledged = True
 
     def handle_reconnect(self, _):
         self.log.warning('Received RECONNECT request, forcing a fresh reconnect')