diff --git a/calibre/viewer.py.json b/calibre/viewer.py.json
index 44c34a2..9bdcf1a 100644
--- a/calibre/viewer.py.json
+++ b/calibre/viewer.py.json
@@ -1,6 +1,7 @@
 {
   "cols_per_screen_landscape": 2,
   "cols_per_screen_migrated": true,
+  "side_margin": 52,
   "background_color": "#f2f0e9",
   "text_color": "#383226",
   "serif_family": "Bookerly",