diff --git a/src/cargo/ops/fix.rs b/src/cargo/ops/fix.rs
index f9e5ce1e8..b020d6bc2 100644
--- a/src/cargo/ops/fix.rs
+++ b/src/cargo/ops/fix.rs
@@ -22,7 +22,6 @@ const FIX_ENV: &str = "__CARGO_FIX_PLZ";
 const BROKEN_CODE_ENV: &str = "__CARGO_FIX_BROKEN_CODE";
 const PREPARE_FOR_ENV: &str = "__CARGO_FIX_PREPARE_FOR";
 const EDITION_ENV: &str = "__CARGO_FIX_EDITION";
-
 const IDIOMS_ENV: &str = "__CARGO_FIX_IDIOMS";
 
 pub struct FixOptions<'a> {
@@ -258,9 +257,10 @@ fn rustfix_crate(
     // process at a time. If two invocations concurrently check a crate then
     // it's likely to corrupt it.
     //
-    // Currently we do this by assigning the name on our lock to the first
-    // argument that looks like a Rust file.
-    let _lock = LockServerClient::lock(&lock_addr.parse()?, filename)?;
+    // Currently we do this by assigning the name on our lock to the manifest
+    // directory.
+    let dir = env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR is missing?");
+    let _lock = LockServerClient::lock(&lock_addr.parse()?, dir)?;
 
     // Next up this is a bit suspicious, but we *iteratively* execute rustc and
     // collect suggestions to feed to rustfix. Once we hit our limit of times to
diff --git a/src/cargo/util/lockserver.rs b/src/cargo/util/lockserver.rs
index 9a0ce39b1..9c4878dfc 100644
--- a/src/cargo/util/lockserver.rs
+++ b/src/cargo/util/lockserver.rs
@@ -14,7 +14,6 @@
 use std::collections::HashMap;
 use std::io::{BufRead, BufReader, Read, Write};
 use std::net::{SocketAddr, TcpListener, TcpStream};
-use std::path::Path;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
 use std::thread::{self, JoinHandle};
@@ -156,11 +155,11 @@ impl Drop for LockServerStarted {
 }
 
 impl LockServerClient {
-    pub fn lock(addr: &SocketAddr, name: &Path) -> Result<LockServerClient, Error> {
+    pub fn lock(addr: &SocketAddr, name: impl AsRef<[u8]>) -> Result<LockServerClient, Error> {
         let mut client = TcpStream::connect(&addr)
             .with_context(|_| "failed to connect to parent lock server")?;
         client
-            .write_all(name.display().to_string().as_bytes())
+            .write_all(name.as_ref())
             .and_then(|_| client.write_all(b"\n"))
             .with_context(|_| "failed to write to lock server")?;
         let mut buf = [0];
diff --git a/tests/testsuite/fix.rs b/tests/testsuite/fix.rs
index d31693a6c..679d47861 100644
--- a/tests/testsuite/fix.rs
+++ b/tests/testsuite/fix.rs
@@ -1235,3 +1235,17 @@ fn fix_to_broken_code() {
         "pub fn foo() { let x = 3; drop(x); }"
     );
 }
+
+#[test]
+fn fix_with_common() {
+    let p = project()
+        .file("src/lib.rs", "")
+        .file("tests/t1.rs", "mod common; #[test] fn t1() { common::try(); }")
+        .file("tests/t2.rs", "mod common; #[test] fn t2() { common::try(); }")
+        .file("tests/common/mod.rs", "pub fn try() {}")
+        .build();
+
+    p.cargo("fix --edition --allow-no-vcs").run();
+
+    assert_eq!(p.read_file("tests/common/mod.rs"), "pub fn r#try() {}");
+}