diff --git a/jetty-openid/src/main/java/org/eclipse/jetty/security/openid/OpenIdConfiguration.java b/jetty-openid/src/main/java/org/eclipse/jetty/security/openid/OpenIdConfiguration.java
index 3d14aa2d36c..f3c9134b4a0 100644
--- a/jetty-openid/src/main/java/org/eclipse/jetty/security/openid/OpenIdConfiguration.java
+++ b/jetty-openid/src/main/java/org/eclipse/jetty/security/openid/OpenIdConfiguration.java
@@ -131,7 +131,8 @@ public class OpenIdConfiguration implements Serializable
 
     public void addScopes(String... scopes)
     {
-        Collections.addAll(this.scopes, scopes);
+        if (scopes != null)
+            Collections.addAll(this.scopes, scopes);
     }
 
     public List<String> getScopes()
diff --git a/jetty-util/src/main/java/org/eclipse/jetty/util/thread/ReservedThreadExecutor.java b/jetty-util/src/main/java/org/eclipse/jetty/util/thread/ReservedThreadExecutor.java
index d34792634ef..eaf4819a96f 100644
--- a/jetty-util/src/main/java/org/eclipse/jetty/util/thread/ReservedThreadExecutor.java
+++ b/jetty-util/src/main/java/org/eclipse/jetty/util/thread/ReservedThreadExecutor.java
@@ -155,6 +155,7 @@ public class ReservedThreadExecutor extends AbstractLifeCycle implements TryExec
     public void doStart() throws Exception
     {
         _lease = ThreadPoolBudget.leaseFrom(getExecutor(), this, _capacity);
+        _size.set(0);
         super.doStart();
     }
 
@@ -163,15 +164,29 @@ public class ReservedThreadExecutor extends AbstractLifeCycle implements TryExec
     {
         if (_lease != null)
             _lease.close();
+
+        super.doStop();
+
         while (true)
         {
+            int size = _size.get();
+            // If no reserved threads left try setting size to -1 to
+            // atomically prevent other threads adding themselves to stack.
+            if (size == 0 && _size.compareAndSet(size, -1))
+                break;
+
             ReservedThread thread = _stack.pollFirst();
             if (thread == null)
-                break;
+            {
+                // Reserved thread must have incremented size but not yet added itself to queue.
+                // We will spin until it is added.
+                Thread.onSpinWait();
+                continue;
+            }
+
             _size.decrementAndGet();
             thread.stop();
         }
-        super.doStop();
     }
 
     @Override
@@ -275,11 +290,12 @@ public class ReservedThreadExecutor extends AbstractLifeCycle implements TryExec
             if (LOG.isDebugEnabled())
                 LOG.debug("{} waiting", this);
 
-            Runnable task = null;
-            while (task == null)
+            while (true)
             {
-                boolean idle = false;
+                if (!isRunning())
+                    return STOP;
 
+                boolean idle = false;
                 try (AutoLock lock = _lock.lock())
                 {
                     if (_task == null)
@@ -296,8 +312,16 @@ public class ReservedThreadExecutor extends AbstractLifeCycle implements TryExec
                             LOG.ignore(e);
                         }
                     }
-                    task = _task;
-                    _task = null;
+                    else
+                    {
+                        Runnable task = _task;
+                        _task = null;
+
+                        if (LOG.isDebugEnabled())
+                            LOG.debug("{} task={}", this, task);
+
+                        return task;
+                    }
                 }
 
                 if (idle)
@@ -312,11 +336,6 @@ public class ReservedThreadExecutor extends AbstractLifeCycle implements TryExec
                     tryExecute(STOP);
                 }
             }
-
-            if (LOG.isDebugEnabled())
-                LOG.debug("{} task={}", this, task);
-
-            return task;
         }
 
         @Override
@@ -329,6 +348,8 @@ public class ReservedThreadExecutor extends AbstractLifeCycle implements TryExec
                 while (true)
                 {
                     int size = _size.get();
+                    if (size < 0)
+                        return;
                     if (size >= _capacity)
                     {
                         if (LOG.isDebugEnabled())
diff --git a/jetty-websocket/jetty-websocket-tests/src/test/java/org/eclipse/jetty/websocket/tests/WriteAfterStopTest.java b/jetty-websocket/jetty-websocket-tests/src/test/java/org/eclipse/jetty/websocket/tests/WriteAfterStopTest.java
index 434e12c90b1..30a7b37431d 100644
--- a/jetty-websocket/jetty-websocket-tests/src/test/java/org/eclipse/jetty/websocket/tests/WriteAfterStopTest.java
+++ b/jetty-websocket/jetty-websocket-tests/src/test/java/org/eclipse/jetty/websocket/tests/WriteAfterStopTest.java
@@ -19,20 +19,16 @@
 package org.eclipse.jetty.websocket.tests;
 
 import java.net.URI;
-import java.nio.channels.ClosedChannelException;
 import java.util.concurrent.TimeUnit;
 
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.ServerConnector;
 import org.eclipse.jetty.servlet.ServletContextHandler;
 import org.eclipse.jetty.servlet.ServletHolder;
-import org.eclipse.jetty.util.log.StacklessLogging;
 import org.eclipse.jetty.websocket.api.Session;
 import org.eclipse.jetty.websocket.api.StatusCode;
 import org.eclipse.jetty.websocket.client.ClientUpgradeRequest;
 import org.eclipse.jetty.websocket.client.WebSocketClient;
-import org.eclipse.jetty.websocket.common.WebSocketSession;
-import org.eclipse.jetty.websocket.core.internal.compress.CompressExtension;
 import org.eclipse.jetty.websocket.server.JettyWebSocketServlet;
 import org.eclipse.jetty.websocket.server.JettyWebSocketServletFactory;
 import org.eclipse.jetty.websocket.server.config.JettyWebSocketServletContainerInitializer;
@@ -108,7 +104,8 @@ public class WriteAfterStopTest
         assertThat(clientSocket.statusCode, is(StatusCode.NORMAL));
         assertThat(serverSocket.statusCode, is(StatusCode.NORMAL));
 
-        ((WebSocketSession)session).stop();
-        assertThrows(IllegalStateException.class, () -> session.getRemote().sendString("hello world"));
+        IllegalStateException failure = assertThrows(IllegalStateException.class,
+            () -> session.getRemote().sendString("this should fail before ExtensionStack"));
+        assertThat(failure.getMessage(), is("CLOSED"));
     }
 }
\ No newline at end of file