diff --git a/ui/src/index.css b/ui/src/index.css
index dc8d71d..140c2fe 100644
--- a/ui/src/index.css
+++ b/ui/src/index.css
@@ -34,6 +34,10 @@ body { margin: 0; background-color: var(--bg-primary); color: var(--text-primary
 
 .dark .bg-white { background-color: var(--bg-secondary); }
 .dark .bg-gray-50 { background-color: var(--bg-tertiary); }
+/* The opacity variant is its own class and the rule above does not reach it, so
+   without this the operation panel's header band stayed light grey in dark mode.
+   --bg-tertiary at the same 60%. */
+.dark .bg-gray-50\/60 { background-color: rgb(59 63 70 / 0.6); }
 .dark .bg-gray-100 { background-color: var(--bg-tertiary); }
 .dark .bg-gray-200 { background-color: var(--bg-tertiary); }
 .dark .bg-gray-300 { background-color: var(--bg-tertiary); }