diff --git a/tests/testcurl.pl b/tests/testcurl.pl
index ef60567d5..8cba54ac9 100755
--- a/tests/testcurl.pl
+++ b/tests/testcurl.pl
@@ -166,7 +166,8 @@ if (($^O eq 'MSWin32') &&
   $confsuffix = '-win32';
 }
 
-
+$ENV{LC_ALL}="C" if (($ENV{LC_ALL}) && ($ENV{LC_ALL} !~ /^C$/));
+$ENV{LC_CTYPE}="C" if (($ENV{LC_CTYPE}) && ($ENV{LC_CTYPE} !~ /^C$/));
 $ENV{LANG}="C";
 
 sub rmtree($) {