diff --git a/lib/puppet/parser/functions/delete_undef_values.rb b/lib/puppet/parser/functions/delete_undef_values.rb
index b41b5f236..9e0408299 100644
--- a/lib/puppet/parser/functions/delete_undef_values.rb
+++ b/lib/puppet/parser/functions/delete_undef_values.rb
@@ -30,9 +30,10 @@ module Puppet::Parser::Functions
     end
     result = args[0].dup
     if result.is_a?(Hash)
-      result.delete_if { |_key, val| val.equal? :undef }
+      result.delete_if { |_, val| val.equal?(:undef) || val.nil? }
     elsif result.is_a?(Array)
       result.delete :undef
+      result.delete nil
     end
     result
   end
diff --git a/spec/functions/delete_undef_values_spec.rb b/spec/functions/delete_undef_values_spec.rb
index be0ebfc88..720a55c8f 100644
--- a/spec/functions/delete_undef_values_spec.rb
+++ b/spec/functions/delete_undef_values_spec.rb
@@ -12,7 +12,6 @@
       describe "when undef is represented by #{undef_value.inspect}" do
         before(:each) do
           pending("review behaviour when being passed undef as #{undef_value.inspect}") if undef_value == ''
-          pending("review behaviour when being passed undef as #{undef_value.inspect}") if undef_value.nil?
         end
         it { is_expected.to run.with_params([undef_value]).and_return([]) }
         it { is_expected.to run.with_params(['one', undef_value, 'two', 'three']).and_return(['one', 'two', 'three']) }
@@ -35,7 +34,6 @@
       describe "when undef is represented by #{undef_value.inspect}" do
         before(:each) do
           pending("review behaviour when being passed undef as #{undef_value.inspect}") if undef_value == ''
-          pending("review behaviour when being passed undef as #{undef_value.inspect}") if undef_value.nil?
         end
         it { is_expected.to run.with_params('key' => undef_value).and_return({}) }
         it {