diff --git a/lib/puppet/parser/functions/rstrip.rb b/lib/puppet/parser/functions/rstrip.rb
deleted file mode 100644
index d07ef6398..000000000
--- a/lib/puppet/parser/functions/rstrip.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-# frozen_string_literal: true
-
-#
-#  rstrip.rb
-#
-module Puppet::Parser::Functions
-  newfunction(:rstrip, type: :rvalue, doc: <<-DOC
-    @summary
-      Strips leading spaces to the right of the string.
-
-    @return
-      the string with leading spaces removed
-
-    > *Note:* from Puppet 6.0.0, the compatible function with the same name in Puppet core
-    will be used instead of this function.
-    DOC
-  ) do |arguments|
-    raise(Puppet::ParseError, "rstrip(): Wrong number of arguments given (#{arguments.size} for 1)") if arguments.empty?
-
-    value = arguments[0]
-
-    unless value.is_a?(Array) || value.is_a?(String)
-      raise(Puppet::ParseError, 'rstrip(): Requires either array or string to work with')
-    end
-
-    result = if value.is_a?(Array)
-               value.map { |i| i.is_a?(String) ? i.rstrip : i }
-             else
-               value.rstrip
-             end
-
-    return result
-  end
-end
-
-# vim: set ts=2 sw=2 et :
diff --git a/spec/functions/rstrip_spec.rb b/spec/functions/rstrip_spec.rb
deleted file mode 100644
index 251fb6677..000000000
--- a/spec/functions/rstrip_spec.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe 'rstrip', if: Puppet::Util::Package.versioncmp(Puppet.version, '6.0.0') < 0 do
-  it { is_expected.not_to eq(nil) }
-  it { is_expected.to run.with_params.and_raise_error(Puppet::ParseError, %r{wrong number of arguments}i) }
-  it {
-    pending('Current implementation ignores parameters after the first.')
-    is_expected.to run.with_params('', '').and_raise_error(Puppet::ParseError, %r{wrong number of arguments}i)
-  }
-  it { is_expected.to run.with_params({}).and_raise_error(Puppet::ParseError, %r{Requires either array or string to work with}) }
-  it { is_expected.to run.with_params(1).and_raise_error(Puppet::ParseError, %r{Requires either array or string to work with}) }
-  it { is_expected.to run.with_params('').and_return('') }
-  it { is_expected.to run.with_params(' ').and_return('') }
-  it { is_expected.to run.with_params('     ').and_return('') }
-  it { is_expected.to run.with_params("\t").and_return('') }
-  it { is_expected.to run.with_params("\t ").and_return('') }
-  it { is_expected.to run.with_params('one').and_return('one') }
-  it { is_expected.to run.with_params(' one').and_return(' one') }
-  it { is_expected.to run.with_params('     one').and_return('     one') }
-  it { is_expected.to run.with_params("\tone").and_return("\tone") }
-  it { is_expected.to run.with_params("\t one").and_return("\t one") }
-  it { is_expected.to run.with_params('one ').and_return('one') }
-  it { is_expected.to run.with_params(' one ').and_return(' one') }
-  it { is_expected.to run.with_params('     one ').and_return('     one') }
-  it { is_expected.to run.with_params(' ǿňè    ').and_return(' ǿňè') }
-  it { is_expected.to run.with_params("\tone ").and_return("\tone") }
-  it { is_expected.to run.with_params("\t one ").and_return("\t one") }
-  it { is_expected.to run.with_params("one\t").and_return('one') }
-  it { is_expected.to run.with_params(" one\t").and_return(' one') }
-  it { is_expected.to run.with_params("     one\t").and_return('     one') }
-  it { is_expected.to run.with_params("\tone\t").and_return("\tone") }
-  it { is_expected.to run.with_params("\t one\t").and_return("\t one") }
-  it { is_expected.to run.with_params(' o n e ').and_return(' o n e') }
-  it { is_expected.to run.with_params(AlsoString.new(' one ')).and_return(' one') }
-end