diff --git a/database/migrations/2018_06_25_101043_add_time_limit_setting_credit_table.php b/database/migrations/2018_06_25_101043_add_time_limit_setting_credit_table.php
index 4e0aefef..7b6b8e41 100644
--- a/database/migrations/2018_06_25_101043_add_time_limit_setting_credit_table.php
+++ b/database/migrations/2018_06_25_101043_add_time_limit_setting_credit_table.php
@@ -14,7 +14,7 @@ class AddTimeLimitSettingCreditTable extends Migration
     public function up()
     {
         Schema::table('setting_credits', function (Blueprint $table) {
-            $table->integer('time_limit');
+            $table->integer('time_limit')->nullable();
         });
     }
 
@@ -26,7 +26,7 @@ class AddTimeLimitSettingCreditTable extends Migration
     public function down()
     {
         Schema::table('setting_credits', function (Blueprint $table) {
-            // $table->dropColumn('time_limit');
+            $table->dropColumn('time_limit');
         });   
     }
 }
\ No newline at end of file