1 files changed, 1 insertions, 1 deletions
diff --git a/lib/dataset.rb b/lib/dataset.rb
index 0a2f770..2b5759e 100644
--- a/lib/dataset.rb
+++ b/lib/dataset.rb
@@ -293,7 +293,7 @@ module OpenTox
       else
         compounds.each do |c|
           features.each do |f|
-            unless @data_entries[c][f]
+            if @data_entries[c]==nil or @data_entries[c][f]==nil
               dataset.add(c,f,nil)
             else
               @data_entries[c][f].each do |v|