diff --git a/src/librustc_mir/transform/check_unsafety.rs b/src/librustc_mir/transform/check_unsafety.rs
index 567fa42c83ae1..9f6b1963ce794 100644
--- a/src/librustc_mir/transform/check_unsafety.rs
+++ b/src/librustc_mir/transform/check_unsafety.rs
@@ -649,6 +649,8 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: DefId) {
             unsafe_unused.push(block_id);
         }
     }
+    // The unused unsafe blocks might not be in source order; sort them so that the unused unsafe
+    // error messages are properly aligned and the issue-45107 and lint-unused-unsafe tests pass.
     unsafe_unused.sort_by_cached_key(|hir_id| tcx.hir().span(*hir_id));
 
     for &block_id in &unsafe_unused {