diff --git a/src/assets/javascripts/observables/header/_/index.ts b/src/assets/javascripts/observables/header/_/index.ts
index 1ff275bce..9f207e1bb 100644
--- a/src/assets/javascripts/observables/header/_/index.ts
+++ b/src/assets/javascripts/observables/header/_/index.ts
@@ -52,7 +52,10 @@ export function watchHeader(
   el: HTMLElement
 ): Observable<Header> {
   const styles = getComputedStyle(el)
-  const sticky = styles.position === "sticky"
+  const sticky = [
+    "sticky",                          /* Modern browsers */
+    "-webkit-sticky"                   /* Old Safari */
+  ].includes(styles.position)
   return of({
     sticky,
     height: sticky ? el.offsetHeight : 0
diff --git a/src/assets/stylesheets/layout/_base.scss b/src/assets/stylesheets/layout/_base.scss
index 23759f89c..0bf2fac08 100644
--- a/src/assets/stylesheets/layout/_base.scss
+++ b/src/assets/stylesheets/layout/_base.scss
@@ -66,6 +66,7 @@ body {
   display: flex;
   position: relative;
   flex-direction: column;
+  width: 100%;
   min-height: 100%;
   // Hack: reset font-size to 10px, so the spacing for all inline elements is
   // correct again. Otherwise the spacing would be based on 20px.