diff --git a/spec/inline_quoted_spec.rb b/spec/inline_quoted_spec.rb
index dc9a8c2..a292bc5 100644
--- a/spec/inline_quoted_spec.rb
+++ b/spec/inline_quoted_spec.rb
@@ -5,7 +5,7 @@
 describe 'Asciidoctor::Epub3::Converter - Inline Quoted' do
   subject { Asciidoctor::Epub3::Converter.new('epub3').convert_inline_quoted node }
 
-  let(:parent) { instance_double(parent).as_null_object }
+  let(:parent) { instance_double('parent').as_null_object }
   let(:node) { Asciidoctor::Inline.new parent, :bar, 'text', type: type }
 
   it 'resolves inline quotes' do