diff --git a/src/tools/compiletest/src/common.rs b/src/tools/compiletest/src/common.rs
index eba02333c8c..55d25fa7c52 100644
--- a/src/tools/compiletest/src/common.rs
+++ b/src/tools/compiletest/src/common.rs
@@ -327,6 +327,9 @@ pub struct Config {
     /// created in `/<build_base>/rustfix_missing_coverage.txt`
     pub rustfix_coverage: bool,
 
+    /// whether to run `tidy` when a rustdoc test fails
+    pub has_tidy: bool,
+
     // Configuration for various run-make tests frobbing things like C compilers
     // or querying about various LLVM component information.
     pub cc: String,
diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index 5177dae8a66..c63bbaf70d3 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -14,7 +14,7 @@ use std::ffi::OsString;
 use std::fs;
 use std::io::{self, ErrorKind};
 use std::path::{Path, PathBuf};
-use std::process::Command;
+use std::process::{Command, Stdio};
 use std::time::SystemTime;
 use test::ColorConfig;
 use tracing::*;
@@ -43,6 +43,10 @@ fn main() {
         panic!("Can't find Valgrind to run Valgrind tests");
     }
 
+    if !config.has_tidy && config.mode == Mode::Rustdoc {
+        eprintln!("warning: `tidy` is not installed; generated diffs will be harder to read");
+    }
+
     log_config(&config);
     run_tests(config);
 }
@@ -189,6 +193,11 @@ pub fn parse_config(args: Vec<String>) -> Config {
 
     let src_base = opt_path(matches, "src-base");
     let run_ignored = matches.opt_present("ignored");
+    let has_tidy = Command::new("tidy")
+        .arg("--version")
+        .stdout(Stdio::null())
+        .status()
+        .map_or(false, |status| status.success());
     Config {
         bless: matches.opt_present("bless"),
         compile_lib_path: make_absolute(opt_path(matches, "compile-lib-path")),
@@ -244,6 +253,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         remote_test_client: matches.opt_str("remote-test-client").map(PathBuf::from),
         compare_mode: matches.opt_str("compare-mode").map(CompareMode::parse),
         rustfix_coverage: matches.opt_present("rustfix-coverage"),
+        has_tidy,
 
         cc: matches.opt_str("cc").unwrap(),
         cxx: matches.opt_str("cxx").unwrap(),
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 398f3e31c6a..d43e75248eb 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2409,32 +2409,22 @@ impl<'test> TestCx<'test> {
             "-modify",
         ];
         let tidy_dir = |dir| {
-            let tidy = |file: &_| {
-                let tidy_proc = Command::new("tidy").args(&tidy_args).arg(file).spawn();
-                match tidy_proc {
-                    Ok(mut proc) => {
-                        proc.wait().unwrap();
-                        true
-                    }
-                    Err(err) => {
-                        eprintln!("failed to run tidy - is it installed? - {}", err);
-                        false
-                    }
-                }
-            };
             for entry in walkdir::WalkDir::new(dir) {
                 let entry = entry.expect("failed to read file");
                 if entry.file_type().is_file()
                     && entry.path().extension().and_then(|p| p.to_str()) == Some("html".into())
                 {
-                    if !tidy(entry.path()) {
-                        return;
-                    }
+                    let status =
+                        Command::new("tidy").args(&tidy_args).arg(entry.path()).status().unwrap();
+                    // `tidy` returns 1 if it modified the file.
+                    assert!(status.success() || status.code() == Some(1));
                 }
             }
         };
-        tidy_dir(out_dir);
-        tidy_dir(&compare_dir);
+        if self.config.has_tidy {
+            tidy_dir(out_dir);
+            tidy_dir(&compare_dir);
+        }
 
         let pager = {
             let output = Command::new("git").args(&["config", "--get", "core.pager"]).output().ok();