Parsing bug linear-gradient

gradient.scss

.test{ background-image: -ms-linear-gradient(top left, #4D303B48 0%, #4D2C3642 100%);}

gradient_generate.rb

bad = []
good = []
index = 0
(0..4294967295).each do |i|
  hex = rand(4294967295).to_s(16).upcase.rjust(8, "0")
  scss= ".test{ background-image: -ms-linear-gradient(##{hex} 0%, ##{hex} 100%);}"
  `echo "#{scss}" | sassc 2>/dev/null`
  if $?.success?
    good << hex
  else
    bad << hex
  end
  index += 1
  if index % 100 == 0
    puts "good: #{good.count}, bad: #{bad.count}"
  end
end

gradient_test.log

$ ~/src/reference/sassc/bin/sassc gradient.scss 
Error: error reading values after  
        on line 1 of gradient.scss
>> round-image: -ms-linear-gradient(top left, #4D303B48 0%, #4D2C3642 100%);}
   ------------------------------------------^

$ ~/src/reference/sassc/bin/sassc -v
sassc: 3.3.0
libsass: 3.3.2-32-gb2a3
sass2scss: 1.0.5