diff --git a/lib/epub/publication/package/guide.rb b/lib/epub/publication/package/guide.rb
index <HASH>..<HASH> 100644
--- a/lib/epub/publication/package/guide.rb
+++ b/lib/epub/publication/package/guide.rb
@@ -30,10 +30,6 @@ module EPUB
           attr_accessor :guide,
                         :type, :title, :href,
                         :iri
-
-          def to_s
-            iri.to_s
-          end
         end
       end
     end
diff --git a/lib/epub/publication/package/manifest.rb b/lib/epub/publication/package/manifest.rb
index <HASH>..<HASH> 100644
--- a/lib/epub/publication/package/manifest.rb
+++ b/lib/epub/publication/package/manifest.rb
@@ -36,10 +36,6 @@ module EPUB
           attr_accessor :manifest,
                         :id, :href, :media_type, :fallback, :properties, :media_overlay,
                         :iri
-
-          def to_s
-            iri.to_s
-          end
         end
       end
     end
Remove #to_s from Publication::Package::Manifest and Guide to help debugging