diff --git a/src/engine/Transaction.c b/src/engine/Transaction.c
index 567a2756b8..259c921dac 100644
--- a/src/engine/Transaction.c
+++ b/src/engine/Transaction.c
@@ -196,7 +196,8 @@ enum
     PROP_DESCRIPTION,
     PROP_CURRENCY,
     PROP_POST_DATE,
-    PROP_ENTER_DATE
+    PROP_ENTER_DATE,
+    PROP_INVOICE,
 };
 
 void
@@ -302,6 +303,9 @@ gnc_transaction_get_property(GObject* object,
                              GParamSpec* pspec)
 {
     Transaction* tx;
+    KvpFrame *frame;
+    gchar *key;
+    GValue *temp;
 
     g_return_if_fail(GNC_IS_TRANSACTION(object));
 
@@ -323,6 +327,10 @@ gnc_transaction_get_property(GObject* object,
     case PROP_ENTER_DATE:
         g_value_set_boxed(value, &tx->date_entered);
         break;
+    case PROP_INVOICE:
+	key = GNC_INVOICE_ID "/" GNC_INVOICE_GUID;
+	qof_instance_get_kvp (QOF_INSTANCE (tx), key, value);
+	break;
     default:
         G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
         break;
@@ -336,6 +344,8 @@ gnc_transaction_set_property(GObject* object,
                              GParamSpec* pspec)
 {
     Transaction* tx;
+    KvpFrame *frame;
+    gchar *key;
 
     g_return_if_fail(GNC_IS_TRANSACTION(object));
 
@@ -357,6 +367,10 @@ gnc_transaction_set_property(GObject* object,
     case PROP_ENTER_DATE:
         xaccTransSetDateEnteredTS(tx, g_value_get_boxed(value));
         break;
+    case PROP_INVOICE:
+	key = GNC_INVOICE_ID "/" GNC_INVOICE_GUID;
+	qof_instance_set_kvp (QOF_INSTANCE (tx), key, value);
+	break;
     default:
         G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
         break;
@@ -425,6 +439,15 @@ gnc_transaction_class_init(TransactionClass* klass)
                         "The date the transaction was entered.",
                         GNC_TYPE_TIMESPEC,
                         G_PARAM_READWRITE));
+
+     g_object_class_install_property(
+       gobject_class,
+        PROP_INVOICE,
+        g_param_spec_boxed("invoice",
+			   "Invoice attached to lot",
+			   "Used by GncInvoice",
+			   GNC_TYPE_GUID,
+			   G_PARAM_READWRITE));
 }
 
 /********************************************************************\
@@ -2594,6 +2617,7 @@ xaccTransFindSplitByAccount(const Transaction *trans, const Account *acc)
     return NULL;
 }
 
+
 /********************************************************************\
 \********************************************************************/
 /* QofObject function implementation */
diff --git a/src/engine/gnc-engine.h b/src/engine/gnc-engine.h
index f4943fba43..1d0deab6cc 100644
--- a/src/engine/gnc-engine.h
+++ b/src/engine/gnc-engine.h
@@ -251,5 +251,10 @@ void gnc_engine_add_commit_error_callback( EngineCommitErrorCallback cb, gpointe
 
 void gnc_engine_signal_commit_error( QofBackendError errcode );
 
+/** STRING CONSTANTS **********************************************
+ * Used to declare constant KVP keys used in more than one class
+ */
+#define GNC_INVOICE_ID    "gncInvoice"
+#define GNC_INVOICE_GUID  "invoice-guid"
 #endif
 /** @} */
diff --git a/src/engine/gncInvoice.c b/src/engine/gncInvoice.c
index 2f41025d98..2ac268f12f 100644
--- a/src/engine/gncInvoice.c
+++ b/src/engine/gncInvoice.c
@@ -1141,10 +1141,8 @@ gncInvoiceAttachToTxn (GncInvoice *invoice, Transaction *txn)
     if (invoice->posted_txn) return;	/* Cannot reset invoice's txn */
 
     xaccTransBeginEdit (txn);
-    kvp = xaccTransGetSlots (txn);
-    value = kvp_value_new_guid (qof_instance_get_guid(QOF_INSTANCE(invoice)));
-    kvp_frame_set_slot_path (kvp, value, GNC_INVOICE_ID, GNC_INVOICE_GUID, NULL);
-    kvp_value_delete (value);
+    qof_instance_set (QOF_INSTANCE (txn), "invoice",
+		      qof_instance_get_guid (QOF_INSTANCE (invoice)), NULL);
     xaccTransSetTxnType (txn, TXN_TYPE_INVOICE);
     xaccTransCommitEdit (txn);
     gncInvoiceSetPostedTxn (invoice, txn);
@@ -1153,19 +1151,13 @@ gncInvoiceAttachToTxn (GncInvoice *invoice, Transaction *txn)
 GncInvoice *
 gncInvoiceGetInvoiceFromTxn (const Transaction *txn)
 {
-    KvpFrame *kvp;
-    KvpValue *value;
     GncGUID *guid;
     QofBook *book;
 
     if (!txn) return NULL;
 
     book = xaccTransGetBook (txn);
-    kvp = xaccTransGetSlots (txn);
-    value = kvp_frame_get_slot_path (kvp, GNC_INVOICE_ID, GNC_INVOICE_GUID, NULL);
-    if (!value) return NULL;
-
-    guid = kvp_value_get_guid (value);
+    qof_instance_get (QOF_INSTANCE (txn), "invoice", &guid, NULL);
     return gncInvoiceLookup(book, guid);
 }
 
diff --git a/src/engine/test/test-engine-kvp-properties.c b/src/engine/test/test-engine-kvp-properties.c
index 9dda2f84a7..ec0f3c5e82 100644
--- a/src/engine/test/test-engine-kvp-properties.c
+++ b/src/engine/test/test-engine-kvp-properties.c
@@ -70,6 +70,13 @@ setup_account (Fixture *fixture, gconstpointer pData)
     fixture->acct = xaccMallocAccount (book);
 }
 
+static void
+setup_trans (Fixture *fixture, gconstpointer pData)
+{
+    QofBook *book = qof_book_new ();
+    fixture->trans = xaccMallocTransaction (book);
+}
+
 static void
 teardown (Fixture *fixture, gconstpointer pData)
 {
@@ -101,7 +108,30 @@ test_account_kvp_properties (Fixture *fixture, gconstpointer pData)
     g_assert (!qof_instance_is_dirty (QOF_INSTANCE (fixture->acct)));
 }
 
+static void
+test_trans_kvp_properties (Fixture *fixture, gconstpointer pData)
+{
+    GncGUID *guid = guid_malloc ();
+    GncGUID *guid_r;
+
+    qof_instance_set (QOF_INSTANCE (fixture->trans),
+		      "invoice", guid,
+		      NULL);
+
+    g_assert (qof_instance_is_dirty (QOF_INSTANCE (fixture->trans)));
+    qof_instance_mark_clean (QOF_INSTANCE (fixture->trans));
+
+    qof_instance_get (QOF_INSTANCE (fixture->trans),
+		      "invoice", &guid_r,
+		      NULL);
+    g_assert (guid_equal (guid, guid_r));
+    g_assert (!qof_instance_is_dirty (QOF_INSTANCE (fixture->trans)));
+    guid_free (guid);
+    guid_free (guid_r);
+}
+
 void test_suite_engine_kvp_properties (void)
 {
     GNC_TEST_ADD (suitename, "Account", Fixture, NULL, setup_account, test_account_kvp_properties, teardown);
+    GNC_TEST_ADD (suitename, "Transaction", Fixture, NULL, setup_trans, test_trans_kvp_properties, teardown);
 }