my ($column) = @_;
my $old = $self->get_column($column);
my $ret = $self->store_column(@_);
- $self->{_dirty_columns}{$column} = 1 unless defined $old && $old eq $ret;
+ $self->{_dirty_columns}{$column} = 1
+ if (defined $old ^ defined $ret) || (defined $old && $old ne $ret);
return $ret;
}