diff --git a/README.md b/README.md
index d0b265a2..bf8187ad 100644
--- a/README.md
+++ b/README.md
@@ -60,7 +60,7 @@ Possible values: `Premium`, `Cracked`, `Unknown`
 
 ## Requirements
 
-* Java 8 supported, but Java 21 recommended for improved threading
+* Java 8 supported, but Java 21+ recommended for improved threading
 * Server software in offlinemode:
   * Spigot (or a fork e.g. Paper) 1.8.8+
     * Protocol plugin:
diff --git a/core/pom.xml b/core/pom.xml
index 093ffd31..c8a26cd8 100644
--- a/core/pom.xml
+++ b/core/pom.xml
@@ -77,14 +77,6 @@
                     </archive>
                 </configuration>
             </plugin>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-compiler-plugin</artifactId>
-                <configuration>
-                    <source>8</source>
-                    <target>8</target>
-                </configuration>
-            </plugin>
         </plugins>
     </build>
 
@@ -98,11 +90,10 @@
                 <pluginManagement>
                     <plugins>
                         <plugin>
-                            <groupId>org.apache.maven.plugins</groupId>
                             <artifactId>maven-compiler-plugin</artifactId>
                             <executions>
                                 <execution>
-                                    <id>jdk9</id>
+                                    <id>jdk21</id>
                                     <goals>
                                         <goal>compile</goal>
                                     </goals>
@@ -116,22 +107,6 @@
                                 </execution>
                             </executions>
                         </plugin>
-                        <plugin>
-                            <groupId>org.apache.maven.plugins</groupId>
-                            <artifactId>maven-jar-plugin</artifactId>
-                            <executions>
-                                <execution>
-                                    <id>default-jar</id>
-                                    <configuration>
-                                        <archive>
-                                            <manifestEntries>
-                                                <Multi-Release>true</Multi-Release>
-                                            </manifestEntries>
-                                        </archive>
-                                    </configuration>
-                                </execution>
-                            </executions>
-                        </plugin>
                     </plugins>
                 </pluginManagement>
             </build>
diff --git a/core/src/test/java/com/github/games647/fastlogin/core/AsyncSchedulerTest.java b/core/src/test/java/com/github/games647/fastlogin/core/AsyncSchedulerTest.java
new file mode 100644
index 00000000..32e49d92
--- /dev/null
+++ b/core/src/test/java/com/github/games647/fastlogin/core/AsyncSchedulerTest.java
@@ -0,0 +1,70 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015-2023 games647 and contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.github.games647.fastlogin.core;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.DisabledForJreRange;
+import org.junit.jupiter.api.condition.EnabledForJreRange;
+import org.junit.jupiter.api.condition.JRE;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+class AsyncSchedulerTest {
+
+    @Test
+    @DisabledForJreRange(min = JRE.JAVA_21)
+    void legacyScheduler() {
+        Logger logger = LoggerFactory.getLogger(AsyncSchedulerTest.class);
+        AsyncScheduler scheduler = new AsyncScheduler(logger, Executors.newCachedThreadPool());
+
+        AtomicBoolean virtual = new AtomicBoolean(false);
+        scheduler.runAsync(() -> setVirtual(virtual)).join();
+
+        Assertions.assertFalse(virtual.get());
+    }
+
+    @Test
+    @EnabledForJreRange(min = JRE.JAVA_21)
+    void greenThread() {
+        Logger logger = LoggerFactory.getLogger(AsyncSchedulerTest.class);
+        AsyncScheduler scheduler = new AsyncScheduler(logger, Executors.newCachedThreadPool());
+
+        AtomicBoolean virtual = new AtomicBoolean(false);
+        scheduler.runAsync(() -> setVirtual(virtual)).join();
+
+        Assertions.assertTrue(virtual.get());
+    }
+
+    private static void setVirtual(AtomicBoolean virtual) {
+        if (Thread.currentThread().isVirtual()) {
+            virtual.set(true);
+        }
+    }
+}
diff --git a/pom.xml b/pom.xml
index b387f545..599d5cff 100644
--- a/pom.xml
+++ b/pom.xml
@@ -157,11 +157,25 @@
             <plugin>
                 <artifactId>maven-surefire-plugin</artifactId>
                 <version>3.2.5</version>
+                <configuration>
+                    <!-- Work-around to make multi-release classes discoverable
+                    https://issues.apache.org/jira/browse/SUREFIRE-1731 -->
+                    <classesDirectory>
+                        ${project.build.directory}/classes/META-INF/versions/21
+                    </classesDirectory>
+                    <additionalClasspathElements>
+                        <additionalClasspathElement>
+                            ${project.build.outputDirectory}
+                        </additionalClasspathElement>
+                    </additionalClasspathElements>
+                </configuration>
             </plugin>
 
             <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-jar-plugin</artifactId>
+                <version>3.4.1</version>
+                <!-- Explicitly enable multi-release for the scheduler,
+                because detection from class shading doesn't work -->
                 <executions>
                     <execution>
                         <id>default-jar</id>