diff --git a/main/render.c b/main/render.c
index d66cc95b5..b03c260a7 100644
--- a/main/render.c
+++ b/main/render.c
@@ -130,8 +130,10 @@ int toggle_show_only_curside(void)
 {
 	return Show_only_curside = !Show_only_curside;
 }
+#endif
 
-void draw_outline(int nverts,const g3s_point **pointlist)
+#ifndef NDEBUG
+static void draw_outline(int nverts,const g3s_point **pointlist)
 {
 	int i;