diff --git a/web/src/routes/Entry/index.tsx b/web/src/routes/Entry/index.tsx
index f8c68faf..408ed67a 100644
--- a/web/src/routes/Entry/index.tsx
+++ b/web/src/routes/Entry/index.tsx
@@ -25,7 +25,7 @@ export const EntryRoute = React.memo(() => {
           <Redirect to="/entry/login" />
         </Switch>
       </div>
-      <div className="flex-1 sm:hidden tc-background" style={{ zIndex: -1 }} />
+      <div className="flex-1 sm:hidden tc-background -z-1" />
     </div>
   );
 });
diff --git a/web/tailwind.config.js b/web/tailwind.config.js
index fc3fcdb7..3cf0d6fb 100644
--- a/web/tailwind.config.js
+++ b/web/tailwind.config.js
@@ -89,6 +89,9 @@ module.exports = {
       transitionProperty: {
         width: 'width',
       },
+      zIndex: {
+        '-1': '-1',
+      },
     },
   },
   variants: {