Index: export_openscad.c
===================================================================
--- export_openscad.c	(revision 21307)
+++ export_openscad.c	(revision 21308)
@@ -132,7 +132,7 @@
 {
 	const char *suffix = ".scad";
 
-	if (PCB)
+	if ((PCB != NULL)  && (openscad_attribute_list[HA_openscadfile].default_val.str_value == NULL))
 		pcb_derive_default_filename(PCB->Filename, &openscad_attribute_list[HA_openscadfile], suffix);
 
 	if (n)