Comment 2 for bug 873598

Here's a patch that seems to fix it.

(venv)trjordan@trjordan-desktop:~/repos/percona-toolkit$ bzr diff -r109..110
=== modified file 'bin/pt-online-schema-change'
--- bin/pt-online-schema-change 2011-09-01 16:00:38 +0000
+++ bin/pt-online-schema-change 2011-10-13 19:13:08 +0000
@@ -3829,7 +3829,7 @@
    my $old_table = "`$db`.`$tbl`";
    my $new_table = "`$db`.`$tmp_tbl`";
    my $new_values = join(', ', map { "NEW.$_" } @{$args{columns}});
- my $columns = join(', ', @{$args{columns}});
+ my $columns = join(', ', map { "`$_`" } @{$args{columns}});

    my $delete_trigger = "CREATE TRIGGER mk_osc_del AFTER DELETE ON $old_table "
                       . "FOR EACH ROW "
@@ -3928,7 +3928,7 @@
    my ($dbh, $msg, $from_table, $to_table, $chunks) = @args{@required_args};
    my $pr = $args{Progress};
    my $sleep = $args{sleep};
- my $columns = join(', ', @{$args{columns}});
+ my $columns = join(', ', map { "`$_`" } @{$args{columns}});
    my $n_chunks = @$chunks - 1;

    for my $chunkno ( 0..$n_chunks ) {