pulling year out of a timestamp - Mailing list pgsql-general

I am trying to perform a join between two tables where I need to join "year" in table 1 with the year component of a
timestampin table 2. 

Something like this:

table1.year = table2.timestamp
where timestamp has the format:  "2009-01-01 00:00:00"

I've tried

date_trunc('year', table2.timestamp) = table1.year

but am getting this error:

ERROR:  operator does not exist: timestamp without time zone = integer
LINE 15:  AND date_trunc('year', _60min_user.time2) = power.year
                                                    ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.

Am I barking up the completely wrong tree?