diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 3ef6e7928fcf389a6a7056439115ce09d9888029..c2c4a5a882441d34e48c7a960c47ff67b8a308ef 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -401,7 +401,7 @@ def type_cast_calculated_value(value, type, operation = nil)
         case operation
         when "count"   then value.to_i
         when "sum"     then type.deserialize(value || 0)
-        when "average" then value.respond_to?(:to_d) ? value.to_d : value
+        when "average" then value&.respond_to?(:to_d) ? value.to_d : value
         else type.deserialize(value)
         end
       end
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index 5b5202d1678cd3325e02e5e2701e546e1d175d6b..ade6b9e8326082cc9d38c181c60fa76661ed3eb3 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -57,12 +57,8 @@ def test_should_return_integer_average_if_db_returns_such
     assert_equal 3, value
   end
 
-  def test_should_return_nil_to_d_as_average
-    if nil.respond_to?(:to_d)
-      assert_equal BigDecimal(0), NumericData.average(:bank_balance)
-    else
-      assert_nil NumericData.average(:bank_balance)
-    end
+  def test_should_return_nil_as_average
+    assert_nil NumericData.average(:bank_balance)
   end
 
   def test_should_get_maximum_of_field