Getting this error on precompiling assets: TypeError: couldn't digest ActiveSupport::StringInquirer

I'm a relatively new Rails programmer, and when I try to precompile assets (or even run the server sometimes), I get this error:

    TypeError: couldn't digest ActiveSupport::StringInquirer

    /Users/Lucia/jruby/lib/ruby/gems/shared/gems/sprockets-3.5.2/lib/sprockets/digest_utils.rb:83:in `digest'
    /Users/Lucia/jruby/lib/ruby/gems/shared/gems/sprockets-3.5.2/lib/sprockets/loader.rb:55:in `block in load'
    /Users/Lucia/jruby/lib/ruby/gems/shared/gems/sprockets-3.5.2/lib/sprockets/loader.rb:312:in `block in fetch_asset_from_dependency_cache'
    org/jruby/RubyArray.java:1560:in `each'
    org/jruby/RubyEnumerable.java:1016:in `each_with_index'
   /Users/Lucia/jruby/lib/ruby/gems/shared/gems/sprockets-3.5.2/lib/sprockets/loader.rb:308:in `fetch_asset_from_dependency_cache'
   /Users/Lucia/jruby/lib/ruby/gems/shared/gems/sprockets-3.5.2/lib/sprockets/loader.rb:44:in `load'

...

I've tried turning off digesting in development, and have tried running the rake task with the RAILS_ENV flag pointing to development, but with no results.

I've tried looking this issue on google, and can't seem to find anything relevant.

I'm running jRuby 9.0.5.0 and rails 4.2.5.2.