Conditional code inside inject could be fatal!

not_so_working_inject.rb

[32] pry(main)> words = %w{mary had a little lamb}                                                                                                                                             
=> ["mary", "had", "a", "little", "lamb"]
[33] pry(main)> total = words.inject(0){ |result, word| word.size + result}                                                                                                                    
=> 18
[34] pry(main)> total = words.inject(0){ |result, word| word.size + result if word.size > 3}                                                                                                   
TypeError: nil can't be coerced into Fixnum
from (pry):52:in `+'
[35] pry(main)>