1 files changed, 4 insertions, 4 deletions
diff --git a/lib/axlsx/drawing/num_data.rb b/lib/axlsx/drawing/num_data.rb
index 79108777..fdcf505c 100644
--- a/lib/axlsx/drawing/num_data.rb
+++ b/lib/axlsx/drawing/num_data.rb
@@ -37,13 +37,13 @@ module Axlsx
 
     # serialize the object
     def to_xml_string(str = +'')
-      str << (+'<c:' << @tag_name.to_s << '>')
-      str << (+'<c:formatCode>' << format_code.to_s << '</c:formatCode>')
-      str << (+'<c:ptCount val="' << @pt.size.to_s << '"/>')
+      str << '<c:' << @tag_name.to_s << '>'
+      str << '<c:formatCode>' << format_code.to_s << '</c:formatCode>'
+      str << '<c:ptCount val="' << @pt.size.to_s << '"/>'
       @pt.each_with_index do |num_val, index|
         num_val.to_xml_string index, str
       end
-      str << (+'</c:' << @tag_name.to_s << '>')
+      str << '</c:' << @tag_name.to_s << '>'
     end
   end
 end