diff --git a/app/assets/stylesheets/framework/zen.scss b/app/assets/stylesheets/framework/zen.scss
index 97ade638db6..0c226ff7598 100644
--- a/app/assets/stylesheets/framework/zen.scss
+++ b/app/assets/stylesheets/framework/zen.scss
@@ -20,8 +20,9 @@
       outline: none;
       resize: none;
       height: 100vh;
+      max-height: calc(100vh - 10px);
       max-width: 900px;
-      margin: 0 auto;
+      margin: 0 auto 10px;
     }
 
     .zen-control-leave {
diff --git a/changelogs/unreleased/28704-fullscreen-zen-mode-is-broken.yml b/changelogs/unreleased/28704-fullscreen-zen-mode-is-broken.yml
new file mode 100644
index 00000000000..b8dba0b5993
--- /dev/null
+++ b/changelogs/unreleased/28704-fullscreen-zen-mode-is-broken.yml
@@ -0,0 +1,4 @@
+---
+title: Set max height to screen height for Zen mode
+merge_request: 9667
+author: