diff --git a/src/themes/basic/_coverpage.styl b/src/themes/basic/_coverpage.styl
index 19ba80666..d0c8d245f 100644
--- a/src/themes/basic/_coverpage.styl
+++ b/src/themes/basic/_coverpage.styl
@@ -15,8 +15,8 @@ section.cover
     opacity 0.8
     position absolute
     top 0
-    height 100%
-    width 100%
+    height 100vh
+    width 100vw
 
   .cover-main
     flex 1