diff --git a/library/kani_macros/src/lib.rs b/library/kani_macros/src/lib.rs
index 491d5c2c9df1..32bd44d2ea38 100644
--- a/library/kani_macros/src/lib.rs
+++ b/library/kani_macros/src/lib.rs
@@ -190,7 +190,7 @@ pub fn modifies(attr: TokenStream, item: TokenStream) -> TokenStream {
 
 /// This module implements Kani attributes in a way that only Kani's compiler can understand.
 /// This code should only be activated when pre-building Kani's sysroot.
-//#[cfg(kani_sysroot)]
+#[cfg(kani_sysroot)]
 mod sysroot {
     use proc_macro_error::{abort, abort_call_site};