diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 6bac05191d14fc40ce15ff03b5bd1b0d949ef3aa..2c210e5ba21aee15483ac711421806c2e9dd0b96 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -539,8 +539,8 @@ def distinct(columns, order_by)
       # ===== Examples
       #  add_timestamps(:suppliers)
       def add_timestamps(table_name)
-        add_column table_name, :created_at, :datetime, :null => false
-        add_column table_name, :updated_at, :datetime, :null => false
+        add_column table_name, :created_at, :datetime
+        add_column table_name, :updated_at, :datetime
       end
 
       # Removes the timestamp columns (created_at and updated_at) from the table definition.