diff --git a/leshan-tl-javacoap-client/src/main/java/org/eclipse/leshan/transport/javacoap/client/endpoint/AbstractJavaCoapClientEndpointsProvider.java b/leshan-tl-javacoap-client/src/main/java/org/eclipse/leshan/transport/javacoap/client/endpoint/AbstractJavaCoapClientEndpointsProvider.java
index 3c0502439a..4f98f45128 100644
--- a/leshan-tl-javacoap-client/src/main/java/org/eclipse/leshan/transport/javacoap/client/endpoint/AbstractJavaCoapClientEndpointsProvider.java
+++ b/leshan-tl-javacoap-client/src/main/java/org/eclipse/leshan/transport/javacoap/client/endpoint/AbstractJavaCoapClientEndpointsProvider.java
@@ -149,15 +149,10 @@ public void add(CoapRequest observeRequest) {
         // Create notification handler
         NotificationHandler notificationHandler = new NotificationHandler(
                 // use router but change Observe request in Read request and also flag request as notification
-                req -> {
-                    TransportContext extendedContext = req.getTransContext() //
-                            .with(LwM2mKeys.LESHAN_NOTIFICATION, true);
-
-                    CoapRequest newReq = new CoapRequest(req.getMethod(), req.getToken(), req.options(),
-                            req.getPayload(), req.getPeerAddress(), extendedContext);
-
-                    return router.apply(newReq.withOptions(coapOptionsBuilder -> coapOptionsBuilder.observe(null)));
-                } //
+                req -> router.apply(req.modify() //
+                        .addContext(LwM2mKeys.LESHAN_NOTIFICATION, true) //
+                        .options(coapOptionsBuilder -> coapOptionsBuilder.observe(null)) //
+                        .build()) //
                 , observersManager);
         objectTree.addListener(notificationHandler);
     }
diff --git a/leshan-tl-javacoap-server/src/main/java/org/eclipse/leshan/transport/javacoap/server/request/CoapRequestBuilder.java b/leshan-tl-javacoap-server/src/main/java/org/eclipse/leshan/transport/javacoap/server/request/CoapRequestBuilder.java
index 95241f24cd..45f616bd8c 100644
--- a/leshan-tl-javacoap-server/src/main/java/org/eclipse/leshan/transport/javacoap/server/request/CoapRequestBuilder.java
+++ b/leshan-tl-javacoap-server/src/main/java/org/eclipse/leshan/transport/javacoap/server/request/CoapRequestBuilder.java
@@ -229,8 +229,8 @@ public void visit(ObserveCompositeRequest request) {
 
         // Add Observation to request context
         coapRequestBuilder //
-                .context(LwM2mKeys.LESHAN_OBSERVATION, observation) //
-                .context(LwM2mKeys.LESHAN_REGISTRATION, registration) //
+                .addContext(LwM2mKeys.LESHAN_OBSERVATION, observation) //
+                .addContext(LwM2mKeys.LESHAN_REGISTRATION, registration) //
                 .token(token);
     }
 
diff --git a/pom.xml b/pom.xml
index 6798f3b65f..65f9ca2036 100644
--- a/pom.xml
+++ b/pom.xml
@@ -124,9 +124,9 @@ Contributors:
     <!-- dependencies version -->
     <californium.version>3.10.0</californium.version>
     <logback.version>1.3.12</logback.version>
-    <javacoap.version>6.19.0</javacoap.version>
+    <javacoap.version>6.21.0</javacoap.version>
     <netty.version>4.1.109.Final</netty.version>
-    <slf4j.api.version>2.0.9</slf4j.api.version>
+    <slf4j.api.version>2.0.13</slf4j.api.version>
     <!-- stuck to 9.4.x for java8 compliance -->
     <jetty.version>9.4.53.v20231009</jetty.version>
     <jackson.version>2.15.3</jackson.version>