Summing negative values doesn't work

I wanted to sum a column that has positive and negative values, and it just added the absolute values. The field is a decimal field, and I configured it to use "Total (Currency)".

For example, if the values are 300, 200, -50, it would summarize as 550 instead of 450.

I changed line 208 in file views_summarize.module from
$total += (float) preg_replace('/[^0-9\.]/', '', $val);
to
$total += (float) preg_replace('/[^-0-9\.]/', '', $val);
adding the "-" to the expression and that seemed to fix it.

I'm not a PHP expert, just at the hacking level and don't totally grok RegEx, so this might not be kosher but it works for me.