diff --git a/lib/puppet/parser/functions/unique.rb b/lib/puppet/parser/functions/unique.rb
deleted file mode 100644
index 7efdaa39e..000000000
--- a/lib/puppet/parser/functions/unique.rb
+++ /dev/null
@@ -1,51 +0,0 @@
-# frozen_string_literal: true
-
-#
-# unique.rb
-#
-module Puppet::Parser::Functions
-  newfunction(:unique, type: :rvalue, doc: <<-DOC
-    @summary
-      This function will remove duplicates from strings and arrays.
-
-    @return
-      String or array with duplicates removed
-
-    @example **Usage**
-
-      unique("aabbcc")
-      Will return: abc
-
-      You can also use this with arrays:
-
-      unique(["a","a","b","b","c","c"])
-      This returns: ["a","b","c"]
-
-    DOC
-  ) do |arguments|
-    if Puppet::Util::Package.versioncmp(Puppet.version, '5.0.0') >= 0
-      function_deprecation([:unique, 'This method is deprecated, please use the core puppet unique function. There is further documentation for the function in the release notes of Puppet 5.0.'])
-    end
-
-    raise(Puppet::ParseError, "unique(): 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, 'unique(): Requires either array or string to work with')
-    end
-
-    result = value.clone
-
-    string = value.is_a?(String) ? true : false
-
-    # We turn any string value into an array to be able to shuffle ...
-    result = string ? result.split('') : result
-    result = result.uniq # Remove duplicates ...
-    result = string ? result.join : result
-
-    return result
-  end
-end
-
-# vim: set ts=2 sw=2 et :
diff --git a/spec/functions/unique_spec.rb b/spec/functions/unique_spec.rb
deleted file mode 100644
index 92234fae0..000000000
--- a/spec/functions/unique_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe 'unique' do
-  if Puppet.version.to_f < 5.0
-    describe 'signature validation' 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([], 'extra').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}) }
-      it { is_expected.to run.with_params(1).and_raise_error(Puppet::ParseError, %r{Requires either array or string to work}) }
-      it { is_expected.to run.with_params(true).and_raise_error(Puppet::ParseError, %r{Requires either array or string to work}) }
-    end
-
-    context 'when called with an array' do
-      it { is_expected.to run.with_params([]).and_return([]) }
-      it { is_expected.to run.with_params(['a']).and_return(['a']) }
-      it { is_expected.to run.with_params(['a', 'b', 'a']).and_return(['a', 'b']) }
-      it { is_expected.to run.with_params(['ã', 'ъ', 'ã']).and_return(['ã', 'ъ']) }
-    end
-
-    context 'when called with a string' do
-      it { is_expected.to run.with_params('').and_return('') }
-      it { is_expected.to run.with_params('a').and_return('a') }
-      it { is_expected.to run.with_params('aaba').and_return('ab') }
-      it { is_expected.to run.with_params('ããъã').and_return('ãъ') }
-    end
-  end
-end