diff --git a/assets/css/010_structure.css b/assets/css/010_structure.css
index 3cf3439..1ca6083 100644
--- a/assets/css/010_structure.css
+++ b/assets/css/010_structure.css
@@ -12,7 +12,7 @@
  ************************/
 
 :root {
-  --content-width: 40em;
+  --content-width: 40rem;
 }
 
 body {