Custom plugin update problem

I am trying to upgrade my custom plugin to logstash 5.
I changed the gemspec of my plugin from "logstash-core", ">= 2.0.0", "< 3.0.0" to "logstash-core-plugin-api", "~> 2.0"
And when I try to run bundle exec rspec I've got this error:

[root@6514d5fec4d4 logstash-filter-dynamic_couchbase]# bundle exec rspec --- jar coordinate com.fasterxml.jackson.core:jackson-annotations already loaded with version 2.7.1 - omit version 2.7.0 --- jar coordinate com.fasterxml.jackson.core:jackson-databind already loaded with version 2.7.1 - omit version 2.7.1-1 Using Accessor#strict_set for specs NameError: undefined method '[]=' for class 'LogStash::Event' alias_method at org/jruby/RubyModule.java:2313 Event at /usr/local/rvm/gems/jruby-1.7.25/gems/logstash-devutils-0.0.18-java/lib/logstash/devutils/rspec/spec_helper.rb:38 (root) at /usr/local/rvm/gems/jruby-1.7.25/gems/logstash-devutils-0.0.18-java/lib/logstash/devutils/rspec/spec_helper.rb:37 require at org/jruby/RubyKernel.java:1040 (root) at /home/application/logstash-filter-dynamic_couchbase/spec/filters/dynamic_couchbase_spec.rb:1 load at org/jruby/RubyKernel.java:1059 (root) at /home/application/logstash-filter-dynamic_couchbase/spec/filters/dynamic_couchbase_spec.rb:1 each at org/jruby/RubyArray.java:1613 (root) at /usr/local/rvm/gems/jruby-1.7.25/gems/rspec-core-3.1.7/lib/rspec/core/configuration.rb:1 load_spec_files at /usr/local/rvm/gems/jruby-1.7.25/gems/rspec-core-3.1.7/lib/rspec/core/configuration.rb:1105 load_spec_files at /usr/local/rvm/gems/jruby-1.7.25/gems/rspec-core-3.1.7/lib/rspec/core/configuration.rb:1105 setup at /usr/local/rvm/gems/jruby-1.7.25/gems/rspec-core-3.1.7/lib/rspec/core/runner.rb:96 run at /usr/local/rvm/gems/jruby-1.7.25/gems/rspec-core-3.1.7/lib/rspec/core/runner.rb:84 run at /usr/local/rvm/gems/jruby-1.7.25/gems/rspec-core-3.1.7/lib/rspec/core/runner.rb:69 load at org/jruby/RubyKernel.java:1059 (root) at /usr/local/rvm/gems/jruby-1.7.25/bin/rspec:23