Failed to execute goal org.asciidoctor:asciidoctor-maven-plugin

[INFO] Infinispan Documentation ........................... FAILURE [01:33 min]
[INFO] Infinispan Doclets ................................. SKIPPED
[INFO] Infinispan JavaDoc Embedded ........................ SKIPPED
[INFO] Infinispan JavaDoc Remote .......................... SKIPPED
[INFO] Infinispan JavaDoc All ............................. SKIPPED
[INFO] Infinispan Distribution ............................ SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 16:35 min
[INFO] Finished at: 2018-09-27T09:10:16-04:00
[INFO] Final Memory: 931M/1703M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.asciidoctor:asciidoctor-maven-plugin:1.5.6:process-asciidoc (pdf) on project infinispan-docs: Execution pdf of goal org.asciidoctor:asciidoctor-maven-plugin:1.5.6:process-asciidoc failed: org.jruby.exceptions.RaiseException: (NoMethodError) undefined method `encoding' for nil:NilClass -> [Help 1]
[ERROR] 
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR] 
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginExecutionException
[ERROR] 
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn <goals> -rf :infinispan-docs
+ '[' 1 '!=' 0 ']'