"Error: invalid byte sequence in UTF-8" file input crash

Getting repeated crashes with the file input, error log looks like this:

{:timestamp=>"2014-04-24T10:11:26.556000+0000", :message=>"A plugin had an unrecoverable error. Will restart this plugin.\n Plugin: <LogStash::Inputs::File type=>\"sfo1-php-errors\", path=>[\"/var/log/php_errors.log\"], sincedb_path=>\"/var/tmp/logstash-php-errors.sincedb\", start_position=>\"end\">\n Error: invalid byte sequence in UTF-8", :level=>:error}

Once this error occurs, the file input plugin re-reads the same line over and over, so the input is effectively stopped. Temp fix is to delete the sincedb file, and restart logstash until the error occurs again.

LS version: 1.4.0

Relevant config lines:

input {
file {
type => "sfo1-php-errors"
path => ["/var/log/php_errors.log"]
sincedb_path => ["/var/tmp/logstash-php-errors.sincedb"]
codec => multiline {
pattern => "^%{PHPTIME} "
patterns_dir => [ "/etc/logstash/patterns" ]
negate => true
what => previous
}
}
}