diff --git a/devtools/client/shared/sourceeditor/codemirror/mozilla.css b/devtools/client/shared/sourceeditor/codemirror/mozilla.css
index 5d478baf3b7e..754750f9a536 100644
--- a/devtools/client/shared/sourceeditor/codemirror/mozilla.css
+++ b/devtools/client/shared/sourceeditor/codemirror/mozilla.css
@@ -2221,6 +2221,26 @@ editor
 .
 cm
 -
+gutter
+.
+cm
+-
+lineNumbers
+{
+user
+-
+select
+:
+none
+;
+}
+.
+cm
+-
+editor
+.
+cm
+-
 foldPlaceholder
 {
 font