diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index eaaa409636..e20cc0e76d 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -253,7 +253,7 @@ module ActiveRecord
 
         select_value = operation_over_aggregate_column(column, operation, distinct)
 
-        column_alias = select_value.alias
+        column_alias = select_value.alias || select_value.to_sql
         relation.select_values = [select_value]
 
         query_builder = relation.arel
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index ec6a319ab5..e886268a72 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -461,7 +461,6 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_equal 7, Company.includes(:contracts).sum(:developer_id)
   end
 
-
   def test_from_option_with_specified_index
     if Edge.connection.adapter_name == 'MySQL' or Edge.connection.adapter_name == 'Mysql2'
       assert_equal Edge.count(:all), Edge.from('edges USE INDEX(unique_edge_index)').count(:all)