diff --git a/modules/book/book.css b/modules/book/book.css
index a8d2136df0cba6282fb3c881c7973ad1a0124a34..3348c0f5abbb5845351fbfdb8dc6d175108a5956 100644
--- a/modules/book/book.css
+++ b/modules/book/book.css
@@ -27,9 +27,6 @@
   display: block;
   float: right;
 }
-#book-outline {
-  min-width: 56em;
-}
 .book-outline-form .form-item {
   margin-top: 0;
   margin-bottom: 0;