diff --git a/main/install/configuration.dist.php b/main/install/configuration.dist.php
index ba5afe3192..bacc44286c 100755
--- a/main/install/configuration.dist.php
+++ b/main/install/configuration.dist.php
@@ -2183,7 +2183,7 @@ INSERT INTO `extra_field` (`extra_field_type`, `field_type`, `variable`, `displa
 
 // Enable skills in subcategory to work independant on assignement
 // Require DB changes:
-// ALTER TABLE gradebook_category ADD allow_skills_by_subcategory tinyint(1) NOT NULL DEFAULT '1';
+// ALTER TABLE gradebook_category ADD allow_skills_by_subcategory tinyint(1) NULL DEFAULT '1';
 // Requires edit Entity GradebookCategory: src/Chamilo/CoreBundle/Entity/GradebookCategory.php uncomment "allowSkillsBySubcategory" variable.
 // Requires uncomment the allowSkillsBySubcategory get and set
 //$_configuration['gradebook_enable_subcategory_skills_independant_assignement'] = false;
diff --git a/src/Chamilo/CoreBundle/Entity/GradebookCategory.php b/src/Chamilo/CoreBundle/Entity/GradebookCategory.php
index 794872567c..6d9884459c 100644
--- a/src/Chamilo/CoreBundle/Entity/GradebookCategory.php
+++ b/src/Chamilo/CoreBundle/Entity/GradebookCategory.php
@@ -125,7 +125,7 @@ class GradebookCategory
      *
      * @var int
      *
-     * @ORM\Column(name="allow_skills_by_subcategory", type="integer", nullable=false)
+     * @ORM\Column(name="allow_skills_by_subcategory", type="integer", nullable=true, options={"default": 1})
      */
     //protected $allowSkillsBySubcategory;