diff --git a/src/bootstrap/setup.rs b/src/bootstrap/setup.rs
index 7eb70de91f8..9811cf163e5 100644
--- a/src/bootstrap/setup.rs
+++ b/src/bootstrap/setup.rs
@@ -582,7 +582,7 @@ fn create_vscode_settings_maybe(config: &Config) -> io::Result<()> {
             Some(false) => {
                 // exists and is not current version or outdated, so back it up
                 let mut backup = vscode_settings.clone();
-                backup.set_extension("bak");
+                backup.set_extension("json.bak");
                 eprintln!("warning: copying `settings.json` to `settings.json.bak`");
                 fs::copy(&vscode_settings, &backup)?;
                 "Updated"