diff --git a/resources/skins.vector.styles/layouts/screen.less b/resources/skins.vector.styles/layouts/screen.less
index da5e86dab..a0816d16b 100644
--- a/resources/skins.vector.styles/layouts/screen.less
+++ b/resources/skins.vector.styles/layouts/screen.less
@@ -190,6 +190,11 @@ body {
 
 // Container logic.
 .mw-page-container {
+	// Setting position and z-index is important as it allows overlays appended to the body tag
+	// to position themselves over the Vector interface. This forms another stacking context for
+	// elements placed inside this element
+	position: relative;
+	z-index: 0;
 	max-width: @max-width-page-container;
 	// Fill the viewport even if the content height is small. This also helps
 	// mitigate a long sidebar overflowing the page container (T257518).