diff --git a/theming/message-viewer.css b/theming/message-viewer.css
index 159649bb..bcd2ff7e 100644
--- a/theming/message-viewer.css
+++ b/theming/message-viewer.css
@@ -46,6 +46,7 @@ hr {
 pre {
     font-family: sans-serif;
     white-space: pre-wrap;
+    margin: 0;
 }
 
 .button {