diff --git a/common/src/main/java/io/netty/util/DomainNameMapping.java b/common/src/main/java/io/netty/util/DomainNameMapping.java
index e0a74dcb9a..b3cf039367 100644
--- a/common/src/main/java/io/netty/util/DomainNameMapping.java
+++ b/common/src/main/java/io/netty/util/DomainNameMapping.java
@@ -137,6 +137,7 @@ public class DomainNameMapping<V> implements Mapping<String, V> {
         return defaultValue;
     }
 
+    @Override
     public String toString() {
         return StringUtil.simpleClassName(this) + "(default: " + defaultValue + ", map: " + map + ')';
     }