diff --git a/src/hnswbuild.c b/src/hnswbuild.c
index e1c3bd6..49a35e6 100644
--- a/src/hnswbuild.c
+++ b/src/hnswbuild.c
@@ -377,7 +377,7 @@ BuildCallback(Relation index, CALLBACK_ITEM_POINTER, Datum *values,
 	/* Add to buildstate or free */
 	if (inserted)
 	{
-		element->value = datumTransfer(element->value, false, -1);
+		element->value = datumCopy(element->value, false, -1);
 		element->loaded = true;
 		buildstate->elements = lappend(buildstate->elements, element);
 	}