diff --git a/20.test/35.temporaryDsystem/10.a/textbook.en.md b/20.test/35.temporaryDsystem/10.a/textbook.en.md
index 5bbce35d5..40beabe4d 100644
--- a/20.test/35.temporaryDsystem/10.a/textbook.en.md
+++ b/20.test/35.temporaryDsystem/10.a/textbook.en.md
@@ -1,10 +1,10 @@
 --
 lessons:
-    - slug: test01-en
+    - slug: test01-Len
       order: 1
-    - slug: test02-en
+    - slug: test02-Len
       order: 2
-    - slug: test03-en
+    - slug: test03-Len
       order: 2
 ---