Grunt-contrib-sass throwing "Could not find variant named" errors

Suddenly my task with grunt-sass is throwing Could not find an option named "sourcemap"

build errors . I am currently installing sass 3.5.1 and using grunt-contrib-sass 1.0.0. Any ideas what might be causing this? Here's the output I see:

Could not find an option named "sourcemap".
Usage: dart-sass <input>
-s, --style         Output style.
                    [expanded (default)]
-c, --[no-]color    Whether to emit terminal colors.
    --[no-]trace    Print full Dart stack traces for exceptions.
-h, --help          Print this usage information.
    --version       Print the version of Dart Sass.
Warning: Exited with error code 64 Used --force, continuing.
Done, but with warnings.
Process terminated with code 0.

      

        
        
        
      

    

And this is not a compilation of CSS. Thoughts?