diff --git a/qpdf/qtest/qpdf.test b/qpdf/qtest/qpdf.test
index b6b33977..e1da340a 100644
--- a/qpdf/qtest/qpdf.test
+++ b/qpdf/qtest/qpdf.test
@@ -1675,6 +1675,7 @@ $n_tests += 4;
     for (my $i = 1; $i <= 201; ++$i)
     {
         open(F, sprintf(">%03d-kfo.pdf", $i)) or die;
+        binmode F;
         print F $content;
         close(F);
     }