diff --git a/browser/base/content/scratchpad.xul b/browser/base/content/scratchpad.xul
index 6271b692794..eca6ee9de80 100644
--- a/browser/base/content/scratchpad.xul
+++ b/browser/base/content/scratchpad.xul
@@ -330,6 +330,7 @@
 </popupset>
 
 <textbox id="scratchpad-textbox"
+         class="monospace"
          multiline="true"
          flex="1"
          context="scratchpad-text-popup"