diff --git a/book.toml b/book.toml
index 12b8cb9..2fe4571 100644
--- a/book.toml
+++ b/book.toml
@@ -41,8 +41,3 @@ heading-split-level = 2
 
 [output.html.print]
 enable = false
-
-[output.theme-ace]
-theme-white = "xcode"
-theme-dark = "monokai"
-optional = true