diff --git a/src/main/java/org/qortal/api/websocket/ChatMessagesWebSocket.java b/src/main/java/org/qortal/api/websocket/ChatMessagesWebSocket.java
index fa860441b..ef04b9504 100644
--- a/src/main/java/org/qortal/api/websocket/ChatMessagesWebSocket.java
+++ b/src/main/java/org/qortal/api/websocket/ChatMessagesWebSocket.java
@@ -94,6 +94,10 @@ public void onWebSocketMessage(Session session, String message) {
 	}
 
 	private void onNotify(Session session, ChatTransactionData chatTransactionData, int txGroupId) {
+		if (chatTransactionData == null)
+			// There has been a group-membership change, but we're not interested
+			return;
+
 		// We only want group-based messages with our txGroupId
 		if (chatTransactionData.getRecipient() != null || chatTransactionData.getTxGroupId() != txGroupId)
 			return;