diff --git a/src/lib.rs b/src/lib.rs
index dee607ca..a7c44420 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3736,6 +3736,8 @@ impl Build {
         if let Some(val) = self.env_cache.read().unwrap().get(v).cloned() {
             return val;
         }
+        // Excluding `PATH` prevents spurious rebuilds on Windows, see
+        // <https://github.com/rust-lang/cc-rs/pull/1215> for details.
         if self.emit_rerun_if_env_changed && !provided_by_cargo(v) && v != "PATH" {
             self.cargo_output
                 .print_metadata(&format_args!("cargo:rerun-if-env-changed={}", v));