diff --git a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ChainingListenableFuture.java b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ChainingListenableFuture.java
index ff3662bb..8e3e3b3d 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ChainingListenableFuture.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ChainingListenableFuture.java
@@ -29,6 +29,7 @@
  * in a {@code UndeclaredThrowableException} so that this class can get
  * access to the cause.
  */
+@Deprecated
 class ChainingListenableFuture<I, O>
     extends AbstractFuture<O> implements Runnable {
 
diff --git a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/DirectExecutor.java b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/DirectExecutor.java
index cf5067ac..c9ec3cf1 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/DirectExecutor.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/DirectExecutor.java
@@ -15,6 +15,8 @@
 package org.jenkinsci.plugins.workflow.support.concurrent;
 
 import com.google.common.annotations.GwtCompatible;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
 import java.util.concurrent.Executor;
 
 /**
@@ -22,6 +24,7 @@
  * execute}.
  */
 @GwtCompatible
+@Restricted(NoExternalUse.class)
 enum DirectExecutor implements Executor {
   INSTANCE;
 
diff --git a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/Futures.java b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/Futures.java
index 38172c37..d0a44f4f 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/Futures.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/Futures.java
@@ -41,6 +41,7 @@
  *
  * @author Guava
  */
+@Deprecated
 public abstract class Futures {
     /**
      * Registers separate success and failure callbacks to be run when the {@code
diff --git a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ListFuture.java b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ListFuture.java
index 4293ad06..0b5cb215 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ListFuture.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/ListFuture.java
@@ -36,6 +36,7 @@
    * each component future to fill out the value in the List when that future
    * completes.
    */
+@Deprecated
 class ListFuture<V> extends AbstractFuture<List<V>> {
     ImmutableList<? extends ListenableFuture<? extends V>> futures;
     final boolean allMustSucceed;
diff --git a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/MoreExecutors.java b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/MoreExecutors.java
index c7887b44..2438ff7b 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/MoreExecutors.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/support/concurrent/MoreExecutors.java
@@ -15,6 +15,8 @@
 package org.jenkinsci.plugins.workflow.support.concurrent;
 
 import com.google.common.annotations.GwtCompatible;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.ThreadFactory;
@@ -30,6 +32,7 @@
  * @since 3.0
  */
 @GwtCompatible(emulated = true)
+@Restricted(NoExternalUse.class)
 public final class MoreExecutors {
   private MoreExecutors() {}