diff --git a/core/themes/olivero/css/components/site-header.css b/core/themes/olivero/css/components/site-header.css
index 6dc7c5162ac392cb68ede3c6eb62f97b5eb85ded..0cc3f984ede6164506f3e9d05908522b937b37cf 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 74774b15ce983aa434301e61f34cec041c991e77..8bfd1f97cee414cfb2971aed1cacd701115af9f9 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;
+}