diff --git a/src/components/composer/standalone_composer/standalone_composer.css b/src/components/composer/standalone_composer/standalone_composer.css
index 9ddcf28f85..679a8c980e 100644
--- a/src/components/composer/standalone_composer/standalone_composer.css
+++ b/src/components/composer/standalone_composer/standalone_composer.css
@@ -7,7 +7,8 @@
     }
 
     &.o-invalid {
-      border-bottom: 2px solid red;
+      border-bottom: 1px solid red !important;
+      background-color: var(--os-alert-danger-bg);
     }
 
     /* As the standalone composer is potentially very small (eg. in a side panel), we remove the scrollbar display */