diff --git a/tests/test-wrap-argv.pl b/tests/test-wrap-argv.pl
index b053f28bf2d30534b6c9c380dc56a886d1cb2a08..6adaef9016cbff70646fbcbf3f46116b4d276a48 100755
--- a/tests/test-wrap-argv.pl
+++ b/tests/test-wrap-argv.pl
@@ -89,7 +89,10 @@ sub rewrap {
         my $nl = join('', @lines);
         my $ol = join('', @orig_lines);
         unless ($nl eq $ol) {
-            print STDERR $ol;
+            open DIFF, "| diff -u $file -" or die "cannot run diff: $!";
+            print DIFF $nl;
+            close DIFF;
+
             print STDERR "Incorrect line wrapping in $file\n";
             print STDERR "Use test-wrap-argv.pl to wrap test data files\n";
             return -1;