diff --git a/launcher/pom.xml b/launcher/pom.xml
index 9b62870..1a84670 100644
--- a/launcher/pom.xml
+++ b/launcher/pom.xml
@@ -44,6 +44,18 @@
       <version>4.13.1</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.graalvm.js</groupId>
+      <artifactId>js</artifactId>
+      <version>20.3.0</version>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.graalvm.js</groupId>
+      <artifactId>js-scriptengine</artifactId>
+      <version>20.3.0</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/launcher/src/test/java/com/threerings/getdown/launcher/ProxyUtilTest.java b/launcher/src/test/java/com/threerings/getdown/launcher/ProxyUtilTest.java
index 43ee670..e21377b 100644
--- a/launcher/src/test/java/com/threerings/getdown/launcher/ProxyUtilTest.java
+++ b/launcher/src/test/java/com/threerings/getdown/launcher/ProxyUtilTest.java
@@ -25,6 +25,10 @@ public class ProxyUtilTest {
     }
 
     @Test public void testPACProxy () throws Exception {
+        // we use the Graal JavaScrip VM for testing, because JDK15 no longer bundles Nashorn, but
+        // it does not support calling back into Java unless we set this compatibility property
+        System.setProperty("polyglot.js.nashorn-compat", "true");
+
         String EXAMPLE0 =
             "function FindProxyForURL(url, host) {\n" +
             "  if (shExpMatch(host, '*.example.com')) { return 'DIRECT'; }\n" +