diff --git a/spring-boot/src/main/java/org/springframework/boot/web/embedded/jetty/JettyWebServer.java b/spring-boot/src/main/java/org/springframework/boot/web/embedded/jetty/JettyWebServer.java
index f25bfe6fba..3d2f7fb223 100644
--- a/spring-boot/src/main/java/org/springframework/boot/web/embedded/jetty/JettyWebServer.java
+++ b/spring-boot/src/main/java/org/springframework/boot/web/embedded/jetty/JettyWebServer.java
@@ -27,6 +27,7 @@ import org.eclipse.jetty.server.NetworkConnector;
 import org.eclipse.jetty.server.Server;
 import org.eclipse.jetty.server.handler.HandlerCollection;
 import org.eclipse.jetty.server.handler.HandlerWrapper;
+import org.eclipse.jetty.util.component.AbstractLifeCycle;
 
 import org.springframework.boot.web.server.PortInUseException;
 import org.springframework.boot.web.server.WebServer;
@@ -83,11 +84,21 @@ public class JettyWebServer implements WebServer {
 	private void initialize() {
 		synchronized (this.monitor) {
 			try {
-				// Cache and clear the connectors to prevent requests being handled before
-				// the application context is ready
+				// Cache the connectors and then remove them to prevent requests being
+				// handled before the application context is ready.
 				this.connectors = this.server.getConnectors();
-				this.server.setConnectors(null);
+				this.server.addBean(new AbstractLifeCycle() {
 
+					@Override
+					protected void doStart() throws Exception {
+						for (Connector connector : JettyWebServer.this.connectors) {
+							Assert.state(connector.isStopped(), "Connector " + connector
+									+ " has been started prematurely");
+						}
+						JettyWebServer.this.server.setConnectors(null);
+					}
+
+				});
 				// Start the server so that the ServletContext is available
 				this.server.start();
 				this.server.setStopAtShutdown(false);
diff --git a/spring-boot/src/test/java/org/springframework/boot/web/embedded/jetty/JettyServletWebServerFactoryTests.java b/spring-boot/src/test/java/org/springframework/boot/web/embedded/jetty/JettyServletWebServerFactoryTests.java
index ddc4b0f357..c354530c78 100644
--- a/spring-boot/src/test/java/org/springframework/boot/web/embedded/jetty/JettyServletWebServerFactoryTests.java
+++ b/spring-boot/src/test/java/org/springframework/boot/web/embedded/jetty/JettyServletWebServerFactoryTests.java
@@ -36,6 +36,7 @@ import org.eclipse.jetty.server.SslConnectionFactory;
 import org.eclipse.jetty.server.handler.HandlerCollection;
 import org.eclipse.jetty.server.handler.HandlerWrapper;
 import org.eclipse.jetty.servlet.ServletHolder;
+import org.eclipse.jetty.util.thread.QueuedThreadPool;
 import org.eclipse.jetty.util.thread.ThreadPool;
 import org.eclipse.jetty.webapp.Configuration;
 import org.eclipse.jetty.webapp.WebAppContext;
@@ -51,6 +52,7 @@ import org.springframework.boot.web.servlet.server.AbstractServletWebServerFacto
 import org.springframework.http.HttpHeaders;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.inOrder;
 import static org.mockito.Mockito.mock;
@@ -277,6 +279,22 @@ public class JettyServletWebServerFactoryTests
 				.isSameAs(threadPool);
 	}
 
+	@Test
+	public void startFailsWhenThreadPoolIsTooSmall() throws Exception {
+		JettyServletWebServerFactory factory = getFactory();
+		factory.addServerCustomizers(new JettyServerCustomizer() {
+
+			@Override
+			public void customize(Server server) {
+				QueuedThreadPool threadPool = server.getBean(QueuedThreadPool.class);
+				threadPool.setMaxThreads(2);
+				threadPool.setMinThreads(2);
+			}
+		});
+		this.thrown.expectCause(instanceOf(IllegalStateException.class));
+		factory.getWebServer().start();
+	}
+
 	@Override
 	@SuppressWarnings("serial")
 	// Workaround for Jetty issue - https://bugs.eclipse.org/bugs/show_bug.cgi?id=470646