CSV.parse unexpected behavior

gistfile1.txt

1.9.3-p545 :002 > headers = "col,is,cool"
 => "col,is,cool" 
1.9.3-p545 :003 > csv = CSV.parse(headers,{headers:true})
 => #<CSV::Table mode:col_or_row row_count:1> 
1.9.3-p545 :004 > tworows = "#{headers}\nabc,def,ghi"
 => "col,is,cool\nabc,def,ghi" 
1.9.3-p545 :005 > other_csv = CSV.parse(tworows,{headers:true})
 => #<CSV::Table mode:col_or_row row_count:2> 
1.9.3-p545 :006 > csv.headers
 => [] #I expect this to be ["col", "is", "cool"]
1.9.3-p545 :007 > other_csv.headers
 => ["col", "is", "cool"] #this is what I expect it to be