diff --git a/libnm-core/tests/test-general.c b/libnm-core/tests/test-general.c
index db261adfec..cdee4c574f 100644
--- a/libnm-core/tests/test-general.c
+++ b/libnm-core/tests/test-general.c
@@ -145,7 +145,6 @@ _dedup_obj_full_equal (const NMDedupMultiObj *obj_a,
 static const NMDedupMultiObjClass dedup_obj_class = {
 	.obj_clone = _dedup_obj_clone,
 	.obj_destroy = _dedup_obj_destroy,
-	.obj_full_equality_allows_different_class = FALSE,
 	.obj_full_hash = _dedup_obj_full_hash,
 	.obj_full_equal = _dedup_obj_full_equal,
 };
diff --git a/shared/nm-utils/nm-dedup-multi.c b/shared/nm-utils/nm-dedup-multi.c
index 9e26065b39..f94bdf853e 100644
--- a/shared/nm-utils/nm-dedup-multi.c
+++ b/shared/nm-utils/nm-dedup-multi.c
@@ -155,6 +155,17 @@ _entry_unpack (const NMDedupMultiEntry *entry,
 
 	nm_assert (NM_IN_SET (*out_lookup_head, FALSE, TRUE));
 	ASSERT_idx_type (*out_idx_type);
+
+	/* for lookup of the head, we allow to omit object, but only
+	 * if the idx_type does not parition the objects. Otherwise, we
+	 * require a obj to compare. */
+	nm_assert (   !*out_lookup_head
+	           || (   *out_obj
+	               || !(*out_idx_type)->klass->idx_obj_partition_equal));
+
+	/* lookup of the object requires always an object. */
+	nm_assert (   *out_lookup_head
+	           || *out_obj);
 }
 
 static guint
@@ -286,6 +297,7 @@ _add (NMDedupMultiIndex *self,
 			break;
 		};
 
+		nm_assert (obj->klass == ((const NMDedupMultiObj *) entry->obj)->klass);
 		if (   obj == entry->obj
 		    || obj->klass->obj_full_equal (obj,
 		                                   entry->obj)) {
@@ -775,24 +787,9 @@ static gboolean
 _dict_idx_objs_equal (const NMDedupMultiObj *obj_a,
                       const NMDedupMultiObj *obj_b)
 {
-	const NMDedupMultiObjClass *klass;
-
-	klass = obj_a->klass;
-
-	/* if the class differs, but at least one of them supports calls with
-	 * differing klass, choose it.
-	 *
-	 * Implementing a klass that can compare equality for multiple
-	 * types is hard to get right. E.g. hash(), equal() and get_ref()
-	 * must all agree so that instances of different types look identical. */
-	if (   klass != obj_b->klass
-	    && !klass->obj_full_equality_allows_different_class) {
-		klass = obj_b->klass;
-		if (!klass->obj_full_equality_allows_different_class)
-			return FALSE;
-	}
-
-	return klass->obj_full_equal (obj_a, obj_b);
+	return    obj_a == obj_b
+	       || (   obj_a->klass == obj_b->klass
+	           && obj_a->klass->obj_full_equal (obj_a, obj_b));
 }
 
 void
diff --git a/shared/nm-utils/nm-dedup-multi.h b/shared/nm-utils/nm-dedup-multi.h
index 77a2fd122d..e44fbe451b 100644
--- a/shared/nm-utils/nm-dedup-multi.h
+++ b/shared/nm-utils/nm-dedup-multi.h
@@ -69,8 +69,6 @@ struct _NMDedupMultiObjClass {
 
 	void (*obj_destroy) (NMDedupMultiObj *obj);
 
-	gboolean obj_full_equality_allows_different_class;
-
 	/* the NMDedupMultiObj can be deduplicated. For that the obj_full_hash()
 	 * and obj_full_equal() compare *all* fields of the object, even minor ones. */
 	guint    (*obj_full_hash)  (const NMDedupMultiObj *obj);
@@ -167,9 +165,10 @@ nm_dedup_multi_idx_type_id_equal (const NMDedupMultiIdxType *idx_type,
                                   /* const NMDedupMultiObj * */ gconstpointer obj_b)
 {
 	nm_assert (idx_type);
-	return idx_type->klass->idx_obj_id_equal (idx_type,
-	                                          obj_a,
-	                                          obj_b);
+	return    obj_a == obj_b
+	       || idx_type->klass->idx_obj_id_equal (idx_type,
+	                                             obj_a,
+	                                             obj_b);
 }
 
 static inline gboolean
@@ -181,9 +180,10 @@ nm_dedup_multi_idx_type_partition_equal (const NMDedupMultiIdxType *idx_type,
 	if (idx_type->klass->idx_obj_partition_equal) {
 		nm_assert (obj_a);
 		nm_assert (obj_b);
-		return idx_type->klass->idx_obj_partition_equal (idx_type,
-		                                                 obj_a,
-		                                                 obj_b);
+		return    obj_a == obj_b
+		       || idx_type->klass->idx_obj_partition_equal (idx_type,
+		                                                    obj_a,
+		                                                    obj_b);
 	}
 	return TRUE;
 }