diff --git a/test-env.in b/test-env.in
index 9d0c8cc414905296220d737efe01ac24e144e592..34f57257d2bab83ad775d6f9308b639b43420d14 100644
--- a/test-env.in
+++ b/test-env.in
@@ -87,6 +87,12 @@ then
     trap "kill $daemon_pid ; rm -rf $NIX_STATE_DIR" EXIT
 fi
 
+# Avoid issues that could stem from l10n, such as language/encoding
+# mismatches.
+unset LANGUAGE
+LC_MESSAGES=C
+export LC_MESSAGES
+
 storedir="@storedir@"
 prefix="@prefix@"
 datarootdir="@datarootdir@"