diff --git a/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/ClientServlet.java b/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/ClientServlet.java
index 83f5e88e62..5583a0813a 100644
--- a/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/ClientServlet.java
+++ b/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/ClientServlet.java
@@ -491,6 +491,10 @@ protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws S
             }
             return;
         }
+
+        // nothing match
+        resp.sendError(HttpServletResponse.SC_BAD_REQUEST, "Invalid path");
+        return;
     }
 
     @Override