diff --git a/test/gc/class_unloading/TestCMSClassUnloadingEnabledHWM.java b/test/gc/class_unloading/TestCMSClassUnloadingEnabledHWM.java
index 508407923f6ae988071cbaeaf07ff6debf1abecd..906ac0ff3c4984637628f9699272bf59e67cfa46 100644
--- a/test/gc/class_unloading/TestCMSClassUnloadingEnabledHWM.java
+++ b/test/gc/class_unloading/TestCMSClassUnloadingEnabledHWM.java
@@ -45,6 +45,7 @@ public class TestCMSClassUnloadingEnabledHWM {
   private static OutputAnalyzer run(boolean enableUnloading) throws Exception {
     ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
       "-Xbootclasspath/a:.",
+      "-XX:+UnlockDiagnosticVMOptions",
       "-XX:+WhiteBoxAPI",
       "-XX:MetaspaceSize=" + MetaspaceSize,
       "-Xmn" + YoungGenSize,
diff --git a/test/gc/class_unloading/TestG1ClassUnloadingHWM.java b/test/gc/class_unloading/TestG1ClassUnloadingHWM.java
index 66142a1db3f0c170419c0b301ae6ac389e1bb756..f4c830ae2b5384cbd059cc7386f4468dcbdb4b5e 100644
--- a/test/gc/class_unloading/TestG1ClassUnloadingHWM.java
+++ b/test/gc/class_unloading/TestG1ClassUnloadingHWM.java
@@ -45,6 +45,7 @@ public class TestG1ClassUnloadingHWM {
   private static OutputAnalyzer run(boolean enableUnloading) throws Exception {
     ProcessBuilder pb = ProcessTools.createJavaProcessBuilder(
       "-Xbootclasspath/a:.",
+      "-XX:+UnlockDiagnosticVMOptions",
       "-XX:+WhiteBoxAPI",
       "-XX:MetaspaceSize=" + MetaspaceSize,
       "-Xmn" + YoungGenSize,