diff --git a/static/css/gitalk.css b/static/css/gitalk.css
index 16a97d1..db648db 100644
--- a/static/css/gitalk.css
+++ b/static/css/gitalk.css
@@ -378,7 +378,7 @@
     min-height: 5.125em;
     max-height: 15em;
     border-radius: 5px;
-    border: 1px solid rgba(0, 0, 0, 0.1);
+    border: 1px solid var(--color-border-default);
     font-size: 0.875em;
     word-wrap: break-word;
     resize: vertical;