diff --git a/app/assets/stylesheets/common/foundation/base.scss b/app/assets/stylesheets/common/foundation/base.scss
index ab3e2cc7911..280a7e1c972 100644
--- a/app/assets/stylesheets/common/foundation/base.scss
+++ b/app/assets/stylesheets/common/foundation/base.scss
@@ -103,6 +103,7 @@ fieldset {
 
 pre code {
   overflow: auto;
+  -moz-tab-size: 4;
   tab-size: 4;
 }