diff --git a/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageContext.java b/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageContext.java
index 93b067110..9fc620e53 100644
--- a/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageContext.java
+++ b/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageContext.java
@@ -391,13 +391,18 @@ public boolean toggleCurrentMarkingFlag() {
     }
 
     public void setHiddenRoots(final ArrayObject theHiddenRoots) {
-        assert hiddenRoots == null && theHiddenRoots.isObjectType();
+        assert hiddenRoots == null && (theHiddenRoots.isObjectType() || isTesting());
         hiddenRoots = theHiddenRoots;
         assert validClassTableRootPages();
     }
 
     /* SpurMemoryManager>>#validClassTableRootPages */
     public boolean validClassTableRootPages() {
+        if (!hiddenRoots.isObjectType()) {
+            assert isTesting(); // Ignore dummy images for testing
+            return true;
+        }
+
         final Object[] hiddenRootsObjects = hiddenRoots.getObjectStorage();
         if (hiddenRootsObjects.length != SqueakImageConstants.CLASS_TABLE_ROOT_SLOTS + SqueakImageConstants.HIDDEN_ROOT_SLOTS) {
             return false;
diff --git a/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageReader.java b/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageReader.java
index a98c1f47f..2bbff14cd 100644
--- a/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageReader.java
+++ b/src/de.hpi.swa.trufflesqueak/src/de/hpi/swa/trufflesqueak/image/SqueakImageReader.java
@@ -439,7 +439,7 @@ private void fillInObjects() {
                 if (obj.needsSqueakClass()) {
                     obj.setSqueakClass(chunk.getSqueakClass());
                 }
-                if (!(obj instanceof ClassObject) && obj.needsSqueakHash()) {
+                if (obj.getSqueakHash() != chunk.getHash()) {
                     obj.setSqueakHash(chunk.getHash());
                 }
                 obj.fillin(chunk);