gem update --system returns "no implicit conversion of nil into String"

Question

Running gem update --system keeps returning error

# gem update --system
    Updating rubygems-update
    ERROR:  While executing gem ... (TypeError)
    no implicit conversion of nil into String

How to fix it?
Verbose: http://pastebin.com/2uBYEMTi

Answer 1

It could be due to incompatible gem versions (Maybe a gem doing Monkey patching?). Can you try to update a single gem?