diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServer.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServer.java
index 64b8e6cb73..a48b973416 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServer.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServer.java
@@ -159,20 +159,36 @@ public class UndertowServletWebServer implements WebServer {
 						.info("Undertow started on port(s) " + getPortsDescription());
 			}
 			catch (Exception ex) {
-				if (findBindException(ex) != null) {
-					List<Port> failedPorts = getConfiguredPorts();
-					List<Port> actualPorts = getActualPorts();
-					failedPorts.removeAll(actualPorts);
-					if (failedPorts.size() == 1) {
-						throw new PortInUseException(
-								failedPorts.iterator().next().getNumber());
+				try {
+					if (findBindException(ex) != null) {
+						List<Port> failedPorts = getConfiguredPorts();
+						List<Port> actualPorts = getActualPorts();
+						failedPorts.removeAll(actualPorts);
+						if (failedPorts.size() == 1) {
+							throw new PortInUseException(
+									failedPorts.iterator().next().getNumber());
+						}
 					}
+					throw new WebServerException("Unable to start embedded Undertow", ex);
+				}
+				finally {
+					stopSilently();
 				}
-				throw new WebServerException("Unable to start embedded Undertow", ex);
 			}
 		}
 	}
 
+	private void stopSilently() {
+		try {
+			if (this.undertow != null) {
+				this.undertow.stop();
+			}
+		}
+		catch (Exception ex) {
+			// Ignore
+		}
+	}
+
 	private BindException findBindException(Exception ex) {
 		Throwable candidate = ex;
 		while (candidate != null) {
diff --git a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowWebServer.java b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowWebServer.java
index 104af8fe4b..22eaa779e5 100644
--- a/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowWebServer.java
+++ b/spring-boot-project/spring-boot/src/main/java/org/springframework/boot/web/embedded/undertow/UndertowWebServer.java
@@ -88,20 +88,36 @@ public class UndertowWebServer implements WebServer {
 						.info("Undertow started on port(s) " + getPortsDescription());
 			}
 			catch (Exception ex) {
-				if (findBindException(ex) != null) {
-					List<UndertowWebServer.Port> failedPorts = getConfiguredPorts();
-					List<UndertowWebServer.Port> actualPorts = getActualPorts();
-					failedPorts.removeAll(actualPorts);
-					if (failedPorts.size() == 1) {
-						throw new PortInUseException(
-								failedPorts.iterator().next().getNumber());
+				try {
+					if (findBindException(ex) != null) {
+						List<UndertowWebServer.Port> failedPorts = getConfiguredPorts();
+						List<UndertowWebServer.Port> actualPorts = getActualPorts();
+						failedPorts.removeAll(actualPorts);
+						if (failedPorts.size() == 1) {
+							throw new PortInUseException(
+									failedPorts.iterator().next().getNumber());
+						}
 					}
+					throw new WebServerException("Unable to start embedded Undertow", ex);
+				}
+				finally {
+					stopSilently();
 				}
-				throw new WebServerException("Unable to start embedded Undertow", ex);
 			}
 		}
 	}
 
+	private void stopSilently() {
+		try {
+			if (this.undertow != null) {
+				this.undertow.stop();
+			}
+		}
+		catch (Exception ex) {
+			// Ignore
+		}
+	}
+
 	private BindException findBindException(Exception ex) {
 		Throwable candidate = ex;
 		while (candidate != null) {
diff --git a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java
index c3e90a0078..324e32edab 100644
--- a/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java
+++ b/spring-boot-project/spring-boot/src/test/java/org/springframework/boot/web/embedded/undertow/UndertowServletWebServerFactoryTests.java
@@ -303,6 +303,9 @@ public class UndertowServletWebServerFactoryTests
 			int blockedPort) {
 		assertThat(ex).isInstanceOf(PortInUseException.class);
 		assertThat(((PortInUseException) ex).getPort()).isEqualTo(blockedPort);
+		Object undertow = ReflectionTestUtils.getField(this.webServer, "undertow");
+		Object worker = ReflectionTestUtils.getField(undertow, "worker");
+		assertThat(worker).isNull();
 	}
 
 }