Sporadic failure when running `gemPrepare` tasks

I seem to be hitting some bug somewhere. Very sporadically. I can't pinpoint when exactly it happens or why. Here's the stacktrace:

> Task :gemPrepare

ERROR:  While executing gem ... (Gem::CommandLineError)
    Please specify at least one gem name (e.g. gem build GEMNAME)
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/command.rb:190:in `get_all_gem_names'
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/command.rb:203:in `get_all_gem_names_and_versions'
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/commands/install_command.rb:219:in `install_gems'
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/commands/install_command.rb:167:in `execute'
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/command.rb:323:in `invoke_with_build_args'
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/command_manager.rb:185:in `process_args'
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/command_manager.rb:149:in `run'
        uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/gem_runner.rb:51:in `run'
        uri:classloader:/META-INF/jruby.home/bin/jgem:21:in `<main>'
        org/jruby/RubyKernel.java:1223:in `load'
        uri:classloader:/META-INF/jruby.home/bin/gem:4:in `<main>'

Happens to all my gemPrepare tasks.

P.S. All seems to work fine even with the error happening though.