diff --git a/12.temporary_ins/65.geometrical-optics/50.simple-elements/20.mirror/20.overview/cheatsheet.en.md b/12.temporary_ins/65.geometrical-optics/50.simple-elements/20.mirror/20.overview/cheatsheet.en.md
index caa3ff82a..4f15c34fa 100644
--- a/12.temporary_ins/65.geometrical-optics/50.simple-elements/20.mirror/20.overview/cheatsheet.en.md
+++ b/12.temporary_ins/65.geometrical-optics/50.simple-elements/20.mirror/20.overview/cheatsheet.en.md
@@ -1,4 +1,4 @@
---
+---
 title: Mirrors
 published: true
 routable: true