diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index 70b7a47bcd5..68f8de15ba2 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -652,7 +652,7 @@ h2.location a {
 }
 
 .top-doc .docblock h2 { font-size: 1.375rem; }
-.top-doc .docblock h3 { font-size: 1.25; }
+.top-doc .docblock h3 { font-size: 1.25rem; }
 .top-doc .docblock h4,
 .top-doc .docblock h5 {
 	font-size: 1.125rem;