diff --git a/tests/cli-tests/cltools/zstdless.sh b/tests/cli-tests/cltools/zstdless.sh
index 61f768862c4..a0697bde644 100755
--- a/tests/cli-tests/cltools/zstdless.sh
+++ b/tests/cli-tests/cltools/zstdless.sh
@@ -7,4 +7,4 @@ zstdless file.zst
 println "+ pass parameters"
 zstdless -N file.zst # This parameter does not produce line #s when piped, but still serves to test that the flag went to less and not zstd
 println "+ bad path"
-zstdless bad.zst
+zstdless bad.zst >&2
diff --git a/tests/cli-tests/run.py b/tests/cli-tests/run.py
index 9bba2ecd1ab..b91aa984145 100755
--- a/tests/cli-tests/run.py
+++ b/tests/cli-tests/run.py
@@ -704,6 +704,7 @@ def setup_zstd_symlink_dir(zstd_symlink_dir: str, zstd: str) -> None:
     env["ZSTDLESS_BIN"] = os.path.abspath(args.zstdless)
     env["COMMON"] = os.path.abspath(os.path.join(args.test_dir, "common"))
     env["PATH"] = bin_dir + ":" + os.getenv("PATH", "")
+    env["LC_ALL"] = "C"
 
     opts = Options(
         env=env,