String#to_i does not work when using string object parsed from a csv file

Question

I'm using CSV class to read a csv file with Ruby.

Here is my code

CSV.foreach('../../../db/data/xxxx.csv') do |row|
  # ...
  row[0].to_i
  # ...
end

File '../../../db/data/xxxx.csv' surely exists. row[0] returns "1". So I expect row[0].to_i to return 1, but row[0].to_i returns 0. I thought it is encoding matter of row[0].encoding, but it returns #<Encoding:UTF-8>.

row[0]
#=> "1"
row[0].class
#=> String
row[0].encoding
#=> Encoding:UTF-8
row[0] == "1"
#=> false

Does anyone help me?