diff --git a/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb b/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb
index de0b93721..40340b09d 100644
--- a/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb
+++ b/lib/active_record/connection_adapters/oracle_enhanced_adapter.rb
@@ -655,7 +655,7 @@ def columns_for_distinct(columns, orders) #:nodoc:
         #
         # It does not construct DISTINCT clause. Just return column names for distinct.
         order_columns = orders.reject(&:blank?).map { |s|
-            s = s.to_sql unless s.is_a?(String)
+            s = visitor.compile(s) unless s.is_a?(String)
             # remove any ASC/DESC modifiers
             s.gsub(/\s+(ASC|DESC)\s*?/i, "")
           }.reject(&:blank?).map.with_index { |column, i|