Index: postgis/lwgeom_box3d.c
===================================================================
--- postgis/lwgeom_box3d.c	(révision 8450)
+++ postgis/lwgeom_box3d.c	(copie de travail)
@@ -345,7 +345,7 @@
 Datum BOX3D_combine(PG_FUNCTION_ARGS)
 {
 	BOX3D *box = (BOX3D*)PG_GETARG_POINTER(0);
-	GSERIALIZED *geom = (GSERIALIZED*)PG_DETOAST_DATUM(PG_GETARG_POINTER(1));
+	GSERIALIZED *geom = PG_GETARG_POINTER(1) ? (GSERIALIZED*)PG_DETOAST_DATUM(PG_GETARG_POINTER(1)) : NULL;
 	LWGEOM *lwgeom = NULL;
 	BOX3D *result = NULL;
 	GBOX gbox;