diff --git a/lib/couchrest/mixins/extended_attachments.rb b/lib/couchrest/mixins/extended_attachments.rb
index dd78644..8dbac45 100644
--- a/lib/couchrest/mixins/extended_attachments.rb
+++ b/lib/couchrest/mixins/extended_attachments.rb
@@ -64,7 +64,7 @@ module CouchRest
         def set_attachment_attr(args)
           content_type = args[:content_type] ? args[:content_type] : get_mime_type(args[:file])
           self['_attachments'][args[:name]] = {
-            'content-type' => content_type,
+            'content_type' => content_type,
             'data'         => encode_attachment(args[:file].read)
           }
         end
diff --git a/spec/couchrest/more/extended_doc_attachment_spec.rb b/spec/couchrest/more/extended_doc_attachment_spec.rb
index e73db96..96a8fa3 100644
--- a/spec/couchrest/more/extended_doc_attachment_spec.rb
+++ b/spec/couchrest/more/extended_doc_attachment_spec.rb
@@ -66,7 +66,7 @@ describe "ExtendedDocument attachments" do
   
     it 'should set the content-type if passed' do
       @obj.create_attachment(:file => @file_ext, :name => @attachment_name, :content_type => @content_type)
-      @obj['_attachments'][@attachment_name]['content-type'].should == @content_type
+      @obj['_attachments'][@attachment_name]['content_type'].should == @content_type
     end
   end
 
@@ -100,7 +100,7 @@ describe "ExtendedDocument attachments" do
       file = File.open(FIXTURE_PATH + '/attachments/README')
       @file.should_not == file
       @obj.update_attachment(:file => file, :name => @attachment_name, :content_type => @content_type)
-      @obj['_attachments'][@attachment_name]['content-type'].should == @content_type
+      @obj['_attachments'][@attachment_name]['content_type'].should == @content_type
     end
   
     it 'should delete an attachment that exists' do