diff --git a/t/pt-mext/pt-mext.t b/t/pt-mext/pt-mext.t
index 73d28080..119af85c 100644
--- a/t/pt-mext/pt-mext.t
+++ b/t/pt-mext/pt-mext.t
@@ -26,7 +26,7 @@ ok(
    no_diff(
       "$cmd -- cat $sample/mext-001.txt",
       "t/pt-mext/samples/mext-001-result.txt",
-      post_pipe => "LOCALE=C sort -k1,1",
+      post_pipe => "LOCALE=en_US.utf8 LANG=en_US.UTF-8 sort -k1,1",
    ),
    "mext-001"
 ) or diag($test_diff);
@@ -35,7 +35,7 @@ ok(
    no_diff(
       "$cmd -r -- cat $sample/mext-002.txt",
       "t/pt-mext/samples/mext-002-result.txt",
-      post_pipe => "LOCALE=C sort -k1,1",
+      post_pipe => "LOCALE=en_US.utf8 LANG=en_US.UTF-8 sort -k1,1",
    ),
    "mext-002 -r"
 ) or diag($test_diff);