Redirecting select() output generates error

This is puzzling and I've no idea what to do to fix it.

The table looks like this:

# select * from concentrations limit 2;
site_nbr | sampdate | medium | form | param | quant | unit | cen | floor | ceiling
----------+------------+---------+-------+-----------+-------+------+-----+-------+---------
10332 | 1979-11-06 | surface | total | inorganic | 0.5 | ug/L | 1 | 0 | 0.5
10332 | 1980-02-07 | surface | total | inorganic | 0.001 | ug/L | 1 | 0 | 0.001

Running this statement within psql works just fine (it's entered as a single
line but wrapped by alpine to fit the line limit):

select param, site_nbr, sampdate, min(quant), max(quant), unit from
concentrations group by param, site_nbr, sampdate, unit order by param,
site_nbr, sampdate, unit;

the output ends this way:

organic | 34198 | 2010-10-21 | 0.02 | 0.025 | ng/L
organic | 34198 | 2011-01-14 | 0.02 | 0.046 | ng/L
(585 rows)

But, when I try to redirect output to a disk file like this,
\o data-summary-by-form.txt
the result is an error:

# select param, site_nbr, sampdate, min(quant), max(quant), unit from concentrations group by param, site_nbr, sampdate, unit order by param, site_nbr, sampdate, unit;
ERROR: syntax error at or near "|"
LINE 1: | 1980-05-08 | 0.5 | 0.5 | ug/L

That line is not number 1 and I don't understand this behavior. Could it
be related to using hyphens in the filename rather than underscores?

Rich