diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs
index d439a8d7de4..cc628aa7463 100644
--- a/library/core/tests/lib.rs
+++ b/library/core/tests/lib.rs
@@ -6,7 +6,7 @@
 #![feature(bool_to_option)]
 #![feature(box_syntax)]
 #![feature(cell_update)]
-#![cfg_attr(bootstrap,feature(cfg_panic))]
+#![cfg_attr(bootstrap, feature(cfg_panic))]
 #![cfg_attr(bootstrap, feature(cfg_target_has_atomic))]
 #![feature(const_assume)]
 #![feature(const_black_box)]