diff --git a/css/chao-theorems.css b/css/chao-theorems.css
index 8169857..c67a99d 100644
--- a/css/chao-theorems.css
+++ b/css/chao-theorems.css
@@ -1,6 +1,7 @@
 .theorem-environment {
   font-style: italic;
   margin-top: 1em;
+  background-color: whitesmoke;
 }
 
 .theorem-header {