diff --git a/src/Listeners/Creating.php b/src/Listeners/Creating.php
index efa2e9b..8432a0d 100644
--- a/src/Listeners/Creating.php
+++ b/src/Listeners/Creating.php
@@ -14,7 +14,7 @@ class Creating
      */
     public function handle($model)
     {
-        if (! $model->isUserstamping()) {
+        if (! $model->isUserstamping() || is_null($model->getCreatedByColumn())) {
             return;
         }
 
diff --git a/src/Listeners/Deleting.php b/src/Listeners/Deleting.php
index dee6d44..0927197 100644
--- a/src/Listeners/Deleting.php
+++ b/src/Listeners/Deleting.php
@@ -14,7 +14,7 @@ class Deleting
      */
     public function handle($model)
     {
-        if (! $model->isUserstamping()) {
+        if (! $model->isUserstamping() || is_null($model->getDeletedByColumn())) {
             return;
         }
 
diff --git a/src/Listeners/Restoring.php b/src/Listeners/Restoring.php
index 99ee318..b9309d9 100644
--- a/src/Listeners/Restoring.php
+++ b/src/Listeners/Restoring.php
@@ -12,7 +12,7 @@ class Restoring
      */
     public function handle($model)
     {
-        if (! $model->isUserstamping()) {
+        if (! $model->isUserstamping() || is_null($model->getDeletedByColumn())) {
             return;
         }
 
diff --git a/src/Listeners/Updating.php b/src/Listeners/Updating.php
index bf75972..9f1188c 100644
--- a/src/Listeners/Updating.php
+++ b/src/Listeners/Updating.php
@@ -14,7 +14,7 @@ class Updating
      */
     public function handle($model)
     {
-        if (! $model->isUserstamping() || is_null(Auth::id())) {
+        if (! $model->isUserstamping() || is_null($model->getUpdatedByColumn()) || is_null(Auth::id())) {
             return;
         }
 
diff --git a/src/Userstamps.php b/src/Userstamps.php
index 55a930a..bb4b47a 100644
--- a/src/Userstamps.php
+++ b/src/Userstamps.php
@@ -86,7 +86,7 @@ public function destroyer()
      */
     public function getCreatedByColumn()
     {
-        return defined('static::CREATED_BY') && ! is_null(static::CREATED_BY) ? static::CREATED_BY : 'created_by';
+        return defined('static::CREATED_BY') ? static::CREATED_BY : 'created_by';
     }
 
     /**
@@ -96,7 +96,7 @@ public function getCreatedByColumn()
      */
     public function getUpdatedByColumn()
     {
-        return defined('static::UPDATED_BY') && ! is_null(static::UPDATED_BY) ? static::UPDATED_BY : 'updated_by';
+        return defined('static::UPDATED_BY') ? static::UPDATED_BY : 'updated_by';
     }
 
     /**
@@ -106,7 +106,7 @@ public function getUpdatedByColumn()
      */
     public function getDeletedByColumn()
     {
-        return defined('static::DELETED_BY') && ! is_null(static::DELETED_BY) ? static::DELETED_BY : 'deleted_by';
+        return defined('static::DELETED_BY') ? static::DELETED_BY : 'deleted_by';
     }
 
     /**
diff --git a/tests/UserstampsTest.php b/tests/UserstampsTest.php
index 1a26ed8..7df9902 100644
--- a/tests/UserstampsTest.php
+++ b/tests/UserstampsTest.php
@@ -230,14 +230,14 @@ public function testCustomColumnNamesAreSupported()
         $this->assertNull($foo->alt_deleted_by);
     }
 
-    public function testNullColumnNamesAreSupported()
+    public function testNullColumnNamesDisableUserstamps()
     {
         $this->app['auth']->loginUsingId(1);
 
         $foo = $this->createFooWithNullColumnNames();
 
-        $this->assertEquals(1, $foo->created_by);
-        $this->assertEquals(1, $foo->updated_by);
+        $this->assertNull($foo->created_by);
+        $this->assertNull($foo->updated_by);
 
         $this->app['auth']->loginUsingId(2);
 
@@ -245,11 +245,11 @@ public function testNullColumnNamesAreSupported()
             'bar' => 'bar',
         ]);
 
-        $this->assertEquals(2, $foo->updated_by);
+        $this->assertNull($foo->updated_by);
 
         $foo->delete();
 
-        $this->assertEquals(2, $foo->deleted_by);
+        $this->assertNull($foo->deleted_by);
 
         $foo->restore();
         $this->assertNull($foo->deleted_by);