lib/MESH/tree.rb in mesh-medical-subject-headings-2.0.1 vs lib/MESH/tree.rb in mesh-medical-subject-headings-2.0.2

@@ -71,11 +71,11 @@
           parts = tree_number.split('.')
           if parts.size > 1
             parts.pop
             parent_tree_number = parts.join '.'
             parent = @by_tree_number[parent_tree_number]
-            heading.parents << parent unless parent.nil?
-            parent.children << heading unless parent.nil?
+            heading.parents << parent unless parent.nil? || heading.parents.include?(parent)
+            parent.children << heading unless parent.nil? || parent.children.include?(heading)
           end
         end
       end
 
     end
\ No newline at end of file