CSV-Filter fails converting Strings to Integer with greater value than 10

Hi Guys,

I have a problem parsing a simple csv-file with logstash and the csv filter.
The parsing works fine until a certain point. I have all fields present that I would exspect. As I want to visualize this data in Kibana especially the numerical data, I did learn from my past experience with logstash that you have to explicit convert your present fields from Strings to Integer.
So far so good.

My filter looks like this:
filter {
csv {
columns => ["project","id","mantis-link","summary","status","category","target_version","relations","relCount"]
separator => ","
skip_empty_columns => "false"
if [relCount] {
mutate {
convert => ["relCount", "integer"]

This works fine.
BUT if the value of the relCount field ist greater than 9, i get a csv-parse failure and I have no clue why. I can reproduce it every single time.

Thanks in advance and I appreciate your help.