diff --git a/transport/src/main/java/io/netty/channel/FailedChannelFuture.java b/transport/src/main/java/io/netty/channel/FailedChannelFuture.java
index e74b2e1373..e92cead8ef 100644
--- a/transport/src/main/java/io/netty/channel/FailedChannelFuture.java
+++ b/transport/src/main/java/io/netty/channel/FailedChannelFuture.java
@@ -24,7 +24,7 @@ import java.util.concurrent.TimeoutException;
  * recommended to use {@link Channel#newFailedFuture(Throwable)}
  * instead of calling the constructor of this future.
  */
-class FailedChannelFuture extends CompleteChannelFuture {
+final class FailedChannelFuture extends CompleteChannelFuture {
 
     private final Throwable cause;
 
diff --git a/transport/src/main/java/io/netty/channel/SucceededChannelFuture.java b/transport/src/main/java/io/netty/channel/SucceededChannelFuture.java
index fa1988eb6e..853d82c69d 100644
--- a/transport/src/main/java/io/netty/channel/SucceededChannelFuture.java
+++ b/transport/src/main/java/io/netty/channel/SucceededChannelFuture.java
@@ -24,7 +24,7 @@ import java.util.concurrent.TimeoutException;
  * recommended to use {@link Channel#newSucceededFuture()} instead of
  * calling the constructor of this future.
  */
-class SucceededChannelFuture extends CompleteChannelFuture {
+final class SucceededChannelFuture extends CompleteChannelFuture {
 
     /**
      * Creates a new instance.