diff --git a/app/views/moderations/index.html.erb b/app/views/moderations/index.html.erb
index 5f80f8ddf..d8e9c2265 100644
--- a/app/views/moderations/index.html.erb
+++ b/app/views/moderations/index.html.erb
@@ -46,6 +46,7 @@
   }
 
   .tag-mod-form form textarea {
+    box-sizing: border-box;
     width: 100%;
     padding: 5px;
     font-size: 17px;
diff --git a/app/views/moderations/mod.html.erb b/app/views/moderations/mod.html.erb
index d904528c8..81163d238 100644
--- a/app/views/moderations/mod.html.erb
+++ b/app/views/moderations/mod.html.erb
@@ -67,6 +67,7 @@
   }
 
   .tag-mod-form form textarea {
+    box-sizing: border-box;
     width: 100%;
     padding: 5px;
     font-size: 17px;