diff --git a/DynareBison.yy b/DynareBison.yy
index 5f108976ee68a6d6a61487508ddcd085f17e0602..a4a0885bcbec49e0a8cdc214842c86deb41e3b69 100644
--- a/DynareBison.yy
+++ b/DynareBison.yy
@@ -2262,7 +2262,7 @@ allowed_graph_formats : EPS
                       | PDF
                         { driver.add_graph_format("pdf"); }
                       | NONE
-                        { driver.add_graph_format("pdf"); }
+                        { driver.add_graph_format("none"); }
                       ;
 list_allowed_graph_formats : allowed_graph_formats
                            | list_allowed_graph_formats COMMA allowed_graph_formats