diff --git a/leshan-integration-tests/src/test/java/org/eclipse/leshan/integration/tests/util/cf/LockstepEndpoint.java b/leshan-integration-tests/src/test/java/org/eclipse/leshan/integration/tests/util/cf/LockstepEndpoint.java
index e62434ec77..86e82f9698 100644
--- a/leshan-integration-tests/src/test/java/org/eclipse/leshan/integration/tests/util/cf/LockstepEndpoint.java
+++ b/leshan-integration-tests/src/test/java/org/eclipse/leshan/integration/tests/util/cf/LockstepEndpoint.java
@@ -51,10 +51,11 @@
 import org.eclipse.californium.core.coap.EmptyMessage;
 import org.eclipse.californium.core.coap.Message;
 import org.eclipse.californium.core.coap.Option;
-import org.eclipse.californium.core.coap.OptionNumberRegistry;
 import org.eclipse.californium.core.coap.Request;
 import org.eclipse.californium.core.coap.Response;
 import org.eclipse.californium.core.coap.Token;
+import org.eclipse.californium.core.coap.option.OptionDefinition;
+import org.eclipse.californium.core.coap.option.StandardOptionRegistry;
 import org.eclipse.californium.core.network.serialization.DataParser;
 import org.eclipse.californium.core.network.serialization.DataSerializer;
 import org.eclipse.californium.core.network.serialization.UdpDataParser;
@@ -718,13 +719,23 @@ public String toString() {
                         final int end = numbers.length - 1;
                         int index = 0;
                         for (; index < end; ++index) {
-                            result.append(OptionNumberRegistry.toString(numbers[index])).append(",");
+                            result.append(getOption(numbers[index])).append(",");
                         }
-                        result.append(OptionNumberRegistry.toString(numbers[index]));
+                        result.append(getOption(numbers[index]));
                     }
                     result.append(']');
                     return result.toString();
                 }
+
+                private String getOption(int optionNumber) {
+                    OptionDefinition definition = StandardOptionRegistry.getDefaultOptionRegistry()
+                            .getDefinitionByNumber(optionNumber);
+                    if (definition != null) {
+                        return definition.toString();
+                    } else {
+                        return String.format("Unknown (%d)", optionNumber);
+                    }
+                }
             });
             return this;
         }
diff --git a/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/log/CoapMessage.java b/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/log/CoapMessage.java
index d69791a6bf..cfefadf336 100644
--- a/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/log/CoapMessage.java
+++ b/leshan-server-demo/src/main/java/org/eclipse/leshan/server/demo/servlet/log/CoapMessage.java
@@ -26,10 +26,11 @@
 import org.eclipse.californium.core.coap.CoAP.Type;
 import org.eclipse.californium.core.coap.EmptyMessage;
 import org.eclipse.californium.core.coap.Option;
-import org.eclipse.californium.core.coap.OptionNumberRegistry;
 import org.eclipse.californium.core.coap.OptionSet;
 import org.eclipse.californium.core.coap.Request;
 import org.eclipse.californium.core.coap.Response;
+import org.eclipse.californium.core.coap.option.OptionDefinition;
+import org.eclipse.californium.core.coap.option.StandardOptionRegistry;
 import org.eclipse.leshan.core.util.Hex;
 
 public class CoapMessage {
@@ -82,7 +83,7 @@ private CoapMessage(boolean incoming, Type type, int mId, String token, OptionSe
             if (!opts.isEmpty()) {
                 Map<String, List<String>> optMap = new HashMap<>();
                 for (Option opt : opts) {
-                    String strOption = OptionNumberRegistry.toString(opt.getNumber());
+                    String strOption = getOption(opt.getNumber());
                     List<String> values = optMap.get(strOption);
                     if (values == null) {
                         values = new ArrayList<>();
@@ -111,4 +112,14 @@ private CoapMessage(boolean incoming, Type type, int mId, String token, OptionSe
             }
         }
     }
+
+    private String getOption(int optionNumber) {
+        OptionDefinition definition = StandardOptionRegistry.getDefaultOptionRegistry()
+                .getDefinitionByNumber(optionNumber);
+        if (definition != null) {
+            return definition.toString();
+        } else {
+            return String.format("Unknown (%d)", optionNumber);
+        }
+    }
 }