diff --git a/src/testutils.rs b/src/testutils.rs
index b9a66fff4..63f086642 100644
--- a/src/testutils.rs
+++ b/src/testutils.rs
@@ -45,6 +45,7 @@ impl TestEnvironment {
         let mut cmd = assert_cmd::Command::cargo_bin("jj").unwrap();
         cmd.current_dir(current_dir);
         cmd.args(args);
+        cmd.env_clear();
         cmd.env("HOME", self.home_dir.to_str().unwrap());
         let timestamp = chrono::DateTime::parse_from_rfc3339("2001-02-03T04:05:06+07:00").unwrap();
         let mut command_number = self.command_number.borrow_mut();