diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs
index 2b23f64732b..04169429949 100644
--- a/library/core/src/str/mod.rs
+++ b/library/core/src/str/mod.rs
@@ -2655,5 +2655,6 @@ impl_fn_for_zst! {
     };
 }
 
+// This is required to make `impl From<&str> for Box<dyn Error>` and `impl<E> From<E> for Box<dyn Error>` not overlap.
 #[stable(feature = "rust1", since = "1.0.0")]
 impl !crate::error::Error for &str {}