diff --git a/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/service/HttpHeaderService.java b/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/service/HttpHeaderService.java
index 0fff37d0a88..277288ba7ae 100644
--- a/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/service/HttpHeaderService.java
+++ b/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/service/HttpHeaderService.java
@@ -16,7 +16,7 @@
 
 package smoketest.jetty.service;
 
-import smoketest.jetty.util.RandomStringUtil;
+import smoketest.jetty.util.StringUtil;
 
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.stereotype.Component;
@@ -28,16 +28,12 @@ public class HttpHeaderService {
 	private int maxHttpResponseHeaderSize;
 
 	/**
-	 * Generates random data. The data is:
-	 * <ol>
-	 * <li>is longer than configured
-	 * <code>server.jetty.max-http-response-header-size</code></li>
-	 * <li>is url encoded by base 64 encode the random value</li>
-	 * </ol>
-	 * @return a base64 encoded string of random bytes
+	 * Generates a header value, which is longer than
+	 * 'server.jetty.max-http-response-header-size'.
+	 * @return the header value
 	 */
 	public String getHeaderValue() {
-		return RandomStringUtil.getRandomBase64EncodedString(this.maxHttpResponseHeaderSize + 1);
+		return StringUtil.repeat('A', this.maxHttpResponseHeaderSize + 1);
 	}
 
 }
diff --git a/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/util/RandomStringUtil.java b/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/util/StringUtil.java
similarity index 66%
rename from spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/util/RandomStringUtil.java
rename to spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/util/StringUtil.java
index eddd0e95106..6ff26e7eb0c 100644
--- a/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/util/RandomStringUtil.java
+++ b/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/main/java/smoketest/jetty/util/StringUtil.java
@@ -16,18 +16,17 @@
 
 package smoketest.jetty.util;
 
-import java.util.Base64;
-import java.util.Random;
+import java.util.Arrays;
 
-public final class RandomStringUtil {
+public final class StringUtil {
 
-	private RandomStringUtil() {
+	private StringUtil() {
 	}
 
-	public static String getRandomBase64EncodedString(int length) {
-		byte[] responseHeader = new byte[length];
-		new Random().nextBytes(responseHeader);
-		return Base64.getEncoder().encodeToString(responseHeader);
+	public static String repeat(char c, int length) {
+		char[] chars = new char[length];
+		Arrays.fill(chars, c);
+		return new String(chars);
 	}
 
 }
diff --git a/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/test/java/smoketest/jetty/SampleJettyApplicationTests.java b/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/test/java/smoketest/jetty/SampleJettyApplicationTests.java
index e21fadb0802..d1c970ad570 100644
--- a/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/test/java/smoketest/jetty/SampleJettyApplicationTests.java
+++ b/spring-boot-tests/spring-boot-smoke-tests/spring-boot-smoke-test-jetty/src/test/java/smoketest/jetty/SampleJettyApplicationTests.java
@@ -21,14 +21,12 @@ import java.nio.charset.StandardCharsets;
 import java.util.zip.GZIPInputStream;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.extension.ExtendWith;
-import smoketest.jetty.util.RandomStringUtil;
+import smoketest.jetty.util.StringUtil;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.test.context.SpringBootTest.WebEnvironment;
-import org.springframework.boot.test.system.OutputCaptureExtension;
 import org.springframework.boot.test.web.client.TestRestTemplate;
 import org.springframework.http.HttpEntity;
 import org.springframework.http.HttpHeaders;
@@ -46,9 +44,9 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Andy Wilkinson
  * @author Florian Storz
  * @author Michael Weidmann
+ * @author Moritz Halbritter
  */
 @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
-@ExtendWith(OutputCaptureExtension.class)
 class SampleJettyApplicationTests {
 
 	@Autowired
@@ -85,7 +83,7 @@ class SampleJettyApplicationTests {
 
 	@Test
 	void testMaxHttpRequestHeaderSize() {
-		String headerValue = RandomStringUtil.getRandomBase64EncodedString(this.maxHttpRequestHeaderSize + 1);
+		String headerValue = StringUtil.repeat('A', this.maxHttpRequestHeaderSize + 1);
 		HttpHeaders headers = new HttpHeaders();
 		headers.add("x-max-request-header", headerValue);
 		HttpEntity<?> httpEntity = new HttpEntity<>(headers);