diff --git a/packages/material-ui/src/Backdrop/Backdrop.js b/packages/material-ui/src/Backdrop/Backdrop.js
index 679aacfe7fedaf..64da5c276c080b 100644
--- a/packages/material-ui/src/Backdrop/Backdrop.js
+++ b/packages/material-ui/src/Backdrop/Backdrop.js
@@ -7,7 +7,8 @@ import Fade from '../Fade';
 export const styles = {
   /* Styles applied to the root element. */
   root: {
-    zIndex: 1,
+    // Improve scrollable dialog support.
+    zIndex: -1,
     position: 'fixed',
     display: 'flex',
     alignItems: 'center',