diff --git a/Cargo.toml b/Cargo.toml
index 9027ab2..9b18db4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -35,7 +35,7 @@ chrono = "0.4"
 structopt = { version = "0.3", optional = true }
 phf = { version = "0.8.0", optional = true }
 includedir = { version = "0.6", optional = true }
-mdbook = { version = "0.4", optional = true } 
+mdbook = { version = "0.4", features = ["search"], optional = true }
 
 [build-dependencies]
 includedir_codegen = { version = "0.6", optional = true }