diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index b0f87593f9532..b84dd956de062 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -19,7 +19,7 @@ fn main() {
     let config = Arc::new(parse_config(env::args().collect()));
 
     if !config.has_tidy && config.mode == Mode::Rustdoc {
-        eprintln!("warning: `tidy` is not installed; diffs will not be generated");
+        eprintln!("warning: `tidy` (html-tidy.org) is not installed; diffs will not be generated");
     }
 
     if !config.profiler_runtime && config.mode == Mode::CoverageRun {