diff --git a/build.rs b/build.rs
index 20fe089..a7e6b2c 100644
--- a/build.rs
+++ b/build.rs
@@ -16,6 +16,7 @@ fn main() {
     }
 
     if version.minor < 53 {
+        // https://github.com/rust-lang/rust/issues/43081
         println!("cargo:rustc-cfg=needs_invalid_span_workaround");
     }
 }