Index: export_openscad.c
===================================================================
--- export_openscad.c	(revision 29449)
+++ export_openscad.c	(revision 29450)
@@ -530,14 +530,19 @@
 	int first;
 	pcb_coord_t lx, ly, x, y;
 
-	if (step < 1)
-		step = 1;
-	if (step > 10)
-		step = 10;
+	if (step >= 0) {
+		if (step < 1) step = 1;
+		if (step > 10) step = 10;
+	}
+	else {
+		if (step > -1) step = -1;
+		if (step < -0) step = -10;
+	}
 
 	/* only recent versions support angle for rotate_extrude(), so use line approximation for now */
 	fprintf(f, "			// line-approx arc %f .. %f by %f\n", start_angle, end_angle, step);
 
+	TODO("use the central arc approximation instead");
 	for(first = 1, a = start_angle; step > 0 ? (a < end_angle) : (a > end_angle); a += step) {
 		x = (double)cx + cos((180-a) / PCB_RAD_TO_DEG) * (double)width;
 		y = (double)cy + sin((180-a) / PCB_RAD_TO_DEG) * (double)height;