diff --git a/app/assets/stylesheets/framework/variables.scss b/app/assets/stylesheets/framework/variables.scss
index f30f296d41f..7808f6d3a25 100644
--- a/app/assets/stylesheets/framework/variables.scss
+++ b/app/assets/stylesheets/framework/variables.scss
@@ -233,7 +233,7 @@ $md-area-border: #ddd;
 /*
  * Code
  */
-$code_font_size: 12px;
+$code_font_size: 90%;
 $code_line_height: 1.6;
 
 /*
diff --git a/changelogs/unreleased/48549-markdown-header-code-does-not-have-the-correct-font-size.yml b/changelogs/unreleased/48549-markdown-header-code-does-not-have-the-correct-font-size.yml
new file mode 100644
index 00000000000..f01f7f3db55
--- /dev/null
+++ b/changelogs/unreleased/48549-markdown-header-code-does-not-have-the-correct-font-size.yml
@@ -0,0 +1,5 @@
+---
+title: fix size of code blocks in headings
+merge_request:
+author:
+type: fixed