diff --git a/leshan-core/src/main/java/leshan/server/lwm2m/resource/RegisterResource.java b/leshan-core/src/main/java/leshan/server/lwm2m/resource/RegisterResource.java
index 4b4a994a..133de85c 100644
--- a/leshan-core/src/main/java/leshan/server/lwm2m/resource/RegisterResource.java
+++ b/leshan-core/src/main/java/leshan/server/lwm2m/resource/RegisterResource.java
@@ -164,6 +164,7 @@ public void handlePOST(CoapExchange exchange) {
                     if (securityInfo != null) {
                         LOG.warn("client {} must connect using DTLS PSK", endpoint);
                         exchange.respond(ResponseCode.BAD_REQUEST, "Client must connect thru DTLS (port 5684)");
+                        return;
                     }
                 }