diff --git a/examples/cover/cover.css b/examples/cover/cover.css
index 177ce03bf0..defba7feb0 100644
--- a/examples/cover/cover.css
+++ b/examples/cover/cover.css
@@ -40,6 +40,7 @@ body {
 .site-wrapper {
   display: table;
   width: 100%;
+  height: 100%; /* For at leat Firefox */
   min-height: 100%;
 }
 .site-wrapper-inner {