diff --git a/core/themes/olivero/css/components/site-header.css b/core/themes/olivero/css/components/site-header.css
index ecbdc1ea9cc..beb3f4ce620 100644
--- a/core/themes/olivero/css/components/site-header.css
+++ b/core/themes/olivero/css/components/site-header.css
@@ -110,3 +110,9 @@
   display: flex;
   justify-content: space-between;
 }
+
+/* Reset width set by layout.css */
+
+body.is-fixed .site-header__inner__container {
+  width: auto;
+}
diff --git a/core/themes/olivero/css/components/site-header.pcss.css b/core/themes/olivero/css/components/site-header.pcss.css
index d1ffafdacbd..1c3f3ceabbb 100644
--- a/core/themes/olivero/css/components/site-header.pcss.css
+++ b/core/themes/olivero/css/components/site-header.pcss.css
@@ -105,3 +105,8 @@ body:not(.is-always-mobile-nav) .site-header__fixable.is-fixed:not(.is-expanded)
   display: flex;
   justify-content: space-between;
 }
+
+/* Reset width set by layout.css */
+body.is-fixed .site-header__inner__container {
+  width: auto;
+}