diff --git a/dialog-polyfill.css b/dialog-polyfill.css
index 3993fc8..6f80fef 100644
--- a/dialog-polyfill.css
+++ b/dialog-polyfill.css
@@ -23,7 +23,7 @@ dialog[open] {
 }
 
 .backdrop {
-  position: absolute;
+  position: fixed;
   background: rgba(0,0,0,0.1);
   top: 0;
   bottom: 0;
diff --git a/tests/backdrop.html b/tests/backdrop.html
index e753363..8588180 100644
--- a/tests/backdrop.html
+++ b/tests/backdrop.html
@@ -11,11 +11,6 @@ dialog {
 }
 
 .backdrop {
-  position: fixed;
-  top: 0;
-  bottom: 0;
-  left: 0;
-  right: 0;
   background-color: rgba(0,255,0,0.5);
 }
 </style>