diff --git a/ghost/admin/app/styles/app-dark.css b/ghost/admin/app/styles/app-dark.css
index 8ebc8d0c10..646e7747d5 100644
--- a/ghost/admin/app/styles/app-dark.css
+++ b/ghost/admin/app/styles/app-dark.css
@@ -329,3 +329,7 @@ input,
     background: var(--lightgrey);
     color: var(--darkgrey);
 }
+
+.CodeMirror .cm-spell-error:not(.cm-url):not(.cm-comment):not(.cm-tag):not(.cm-word) {
+    background: rgba(255, 0, 0, .30);
+}