diff --git a/http-api/src/main/java/net/runelite/http/api/ws/messages/party/UserJoin.java b/http-api/src/main/java/net/runelite/http/api/ws/messages/party/UserJoin.java
index 81abe76827..7f940e8060 100644
--- a/http-api/src/main/java/net/runelite/http/api/ws/messages/party/UserJoin.java
+++ b/http-api/src/main/java/net/runelite/http/api/ws/messages/party/UserJoin.java
@@ -34,5 +34,6 @@ import net.runelite.http.api.ws.WebsocketMessage;
 public class UserJoin extends WebsocketMessage
 {
 	private final UUID memberId;
+	private final UUID partyId;
 	private final String name;
 }
diff --git a/runelite-client/src/main/java/net/runelite/client/ws/PartyService.java b/runelite-client/src/main/java/net/runelite/client/ws/PartyService.java
index 47e9c18148..caec527320 100644
--- a/runelite-client/src/main/java/net/runelite/client/ws/PartyService.java
+++ b/runelite-client/src/main/java/net/runelite/client/ws/PartyService.java
@@ -114,6 +114,13 @@ public class PartyService
 	@Subscribe
 	public void onUserJoin(final UserJoin message)
 	{
+		if (!partyId.equals(message.getPartyId()))
+		{
+			// This can happen when a session is resumed server side after the client party
+			// changes when disconnected.
+			return;
+		}
+
 		final PartyMember partyMember = new PartyMember(message.getMemberId(), message.getName());
 		members.add(partyMember);