diff --git a/lib/or_tools/expression.rb b/lib/or_tools/expression.rb
index dffb5ee..fa7b287 100644
--- a/lib/or_tools/expression.rb
+++ b/lib/or_tools/expression.rb
@@ -15,7 +15,7 @@ def -@
     end
 
     def *(other)
-      Expression.new([Product.new(self, Expression.to_expression(other))])
+      Product.new(self, Expression.to_expression(other))
     end
 
     def >(other)