diff --git a/src/util/virobject.c b/src/util/virobject.c
index 3b28331ba7..919519735a 100644
--- a/src/util/virobject.c
+++ b/src/util/virobject.c
@@ -78,6 +78,7 @@ virObjectOnceInit(void)
     if (!(virObjectClass = virClassNew(NULL,
                                        "virObject",
                                        sizeof(virObject),
+                                       0,
                                        NULL)))
         return -1;
 
@@ -159,6 +160,7 @@ virClassPtr
 virClassNew(virClassPtr parent,
             const char *name,
             size_t objectSize,
+            size_t parentSize,
             virObjectDisposeCallback dispose)
 {
     virClassPtr klass;
@@ -167,10 +169,11 @@ virClassNew(virClassPtr parent,
         STRNEQ(name, "virObject")) {
         virReportInvalidNonNullArg(parent);
         return NULL;
-    } else if (parent &&
-               objectSize <= parent->objectSize) {
+    } else if (objectSize <= parentSize ||
+               parentSize != (parent ? parent->objectSize : 0)) {
+        sa_assert(parent);
         virReportInvalidArg(objectSize,
-                            _("object size %zu of %s is smaller than parent class %zu"),
+                            _("object size %zu of %s is not larger than parent class %zu"),
                             objectSize, name, parent->objectSize);
         return NULL;
     }
diff --git a/src/util/virobject.h b/src/util/virobject.h
index d4ec943a43..757068fcc1 100644
--- a/src/util/virobject.h
+++ b/src/util/virobject.h
@@ -82,12 +82,15 @@ virClassPtr virClassForObjectRWLockable(void);
  */
 # define VIR_CLASS_NEW(name, prnt) \
     verify_expr(offsetof(name, parent) == 0, \
-      (name##Class = virClassNew(prnt, #name, sizeof(name), name##Dispose)))
+      (name##Class = virClassNew(prnt, #name, sizeof(name), \
+                                 sizeof(((name *)NULL)->parent), \
+                                 name##Dispose)))
 
 virClassPtr
 virClassNew(virClassPtr parent,
             const char *name,
             size_t objectSize,
+            size_t parentSize,
             virObjectDisposeCallback dispose)
     VIR_PARENT_REQUIRED ATTRIBUTE_NONNULL(2);