Facebook Connect Error "facebooker.rb:57:in `[]=': can't convert Bignum into String"

I was implementing facebook login feature in one of old project developed in Rails 2.3.5. I tried to use authlogic_facebook_connect plugin but with facebooker gem not with facebooker2. I followed a nice blog by Waseem - http://babygnu.blogspot.in/2010/02/facebook-connect-using-facebooker-on.html and did all the settings.
But, when i ran my application using "ruby script/server" it thrown a error :-
/var/lib/gems/1.8/gems/facebooker-1.0.75/lib/facebooker.rb:57:in `[]=': can't convert Bignum into String (TypeError)

Then, I inspect the line 57 in the facebooker.rb file and found that we need to pass "api_key: '' " in string in config/facebooker.yml file and it resolved the issue.

Thanks :-)