diff --git a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/image/DisallowedImageHeapObjects.java b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/image/DisallowedImageHeapObjects.java
index 7cd03ceed323..125efc0dba22 100644
--- a/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/image/DisallowedImageHeapObjects.java
+++ b/substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/image/DisallowedImageHeapObjects.java
@@ -81,8 +81,8 @@ public static void check(Object obj, DisallowedObjectReporter reporter) {
                 // allowed unless the thread is mounted, in which case it references its carrier
                 // thread and fails
             } else if (asThread.getState() != Thread.State.NEW && asThread.getState() != Thread.State.TERMINATED) {
-                throw reporter.raise("Detected a started Thread in the image heap. " +
-                                "Threads running in the image generator are no longer running at image runtime.",
+                throw reporter.raise("Detected a started Thread in the image heap. Thread name: " + asThread.getName() +
+                                ". Threads running in the image generator are no longer running at image runtime.",
                                 asThread, "Prevent threads from starting during image generation, or a started thread from being included in the image.");
             }
         }
diff --git a/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java b/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java
index 53f8025b360f..371c02f56871 100644
--- a/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java
+++ b/substratevm/src/com.oracle.svm.graal.hotspot.libgraal/src/com/oracle/svm/graal/hotspot/libgraal/LibGraalSubstitutions.java
@@ -24,6 +24,7 @@
  */
 package com.oracle.svm.graal.hotspot.libgraal;
 
+import java.lang.ref.ReferenceQueue;
 import java.util.Map;
 
 import com.oracle.svm.core.annotate.Alias;
@@ -40,7 +41,8 @@ public final class LibGraalSubstitutions {
 @TargetClass(value = Services.class, onlyWith = LibGraalFeature.IsEnabled.class)
 final class Target_jdk_vm_ci_services_Services {
     // Checkstyle: stop
-    @Alias @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.FromAlias, isFinal = true)//
+    @Alias //
+    @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.FromAlias, isFinal = true)//
     public static boolean IS_IN_NATIVE_IMAGE = true;
     // Checkstyle: resume
 
@@ -49,13 +51,22 @@ final class Target_jdk_vm_ci_services_Services {
      * requires a larger JVMCI change because the annotation is not visible in that project, so we
      * use this substitution instead.
      */
-    @Alias @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.Reset) //
+    @Alias //
+    @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.Reset) //
     private static Map<String, String> savedProperties;
 }
 
+@TargetClass(className = "jdk.vm.ci.hotspot.Cleaner", onlyWith = LibGraalFeature.IsEnabled.class)
+final class Target_jdk_vm_ci_hotspot_Cleaner {
+    @Alias //
+    @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.NewInstance, isFinal = true, declClass = ReferenceQueue.class)//
+    private static ReferenceQueue<Object> queue;
+}
+
 @TargetClass(className = "jdk.vm.ci.hotspot.HotSpotJDKReflection", onlyWith = LibGraalFeature.IsEnabled.class)
 final class Target_jdk_vm_ci_hotspot_HotSpotJDKReflection {
 
-    @Alias @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.None)//
+    @Alias //
+    @RecomputeFieldValue(kind = RecomputeFieldValue.Kind.None)//
     private long oopSizeOffset;
 }
diff --git a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/GraalGraphObjectReplacer.java b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/GraalGraphObjectReplacer.java
index 3b7474c85ba4..6ede186211f4 100644
--- a/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/GraalGraphObjectReplacer.java
+++ b/substratevm/src/com.oracle.svm.graal/src/com/oracle/svm/graal/hosted/GraalGraphObjectReplacer.java
@@ -112,6 +112,8 @@ public class GraalGraphObjectReplacer implements Function<Object, Object> {
     private final Field substrateTypeRawAllInstanceFieldsField;
     private final Field substrateMethodImplementationsField;
 
+    private final Class<?> jvmciCleanerClass = ReflectionUtil.lookupClass(false, "jdk.vm.ci.hotspot.Cleaner");
+
     /**
      * Tracks whether it is legal to create new types.
      */
@@ -160,7 +162,7 @@ public Object apply(Object source) {
             HotSpotBackendFactory factory = (HotSpotBackendFactory) source;
             Architecture hostArch = HotSpotJVMCIRuntime.runtime().getHostJVMCIBackend().getTarget().arch;
             if (!factory.getArchitecture().equals(hostArch.getClass())) {
-                throw new UnsupportedFeatureException("Non-host archtecture HotSpotBackendFactory should not appear in the image: " + source);
+                throw new UnsupportedFeatureException("Non-host architecture HotSpotBackendFactory should not appear in the image: " + source);
             }
         } else if (source instanceof GraalRuntime) {
             dest = sGraalRuntime;
@@ -201,7 +203,11 @@ public Object apply(Object source) {
         }
 
         assert dest != null;
-        String className = dest.getClass().getName();
+        Class<?> destClass = dest.getClass();
+        if (jvmciCleanerClass.isAssignableFrom(destClass)) {
+            throw new UnsupportedFeatureException(jvmciCleanerClass.getName() + " objects should not appear in the image: " + source);
+        }
+        String className = destClass.getName();
         assert SubstrateUtil.isBuildingLibgraal() || !className.contains(".hotspot.") || className.contains(".svm.jtt.hotspot.") : "HotSpot object in image " + className;
         assert !className.contains(".graal.reachability") : "Analysis meta object in image " + className;
         assert !className.contains(".pointsto.meta.") : "Analysis meta object in image " + className;