diff --git a/core/collector.class.inc.php b/core/collector.class.inc.php
index 3b4d624..8d4acab 100644
--- a/core/collector.class.inc.php
+++ b/core/collector.class.inc.php
@@ -594,7 +594,7 @@ protected function AddRow($aRow)
 	{
 		$aData = array();
 		foreach ($this->aCSVHeaders as $sHeader) {
-			if (is_null($aRow[$sHeader]) && $this->AttributeIsNullified($sHeader)) {
+			if (strlen($aRow[$sHeader])==0 && $this->AttributeIsNullified($sHeader)) {
 				$aData[] = NULL_VALUE;
 			} else {
 				$aData[] = $aRow[$sHeader];
diff --git a/test/CollectorTest.php b/test/CollectorTest.php
index 67004b5..49a72c2 100644
--- a/test/CollectorTest.php
+++ b/test/CollectorTest.php
@@ -109,15 +109,19 @@ public function testAttributeIsNullified($sCollectorXmlSubSection, $bExpectedIsN
 
 		$this->assertEquals($bExpectedIsNullified, $oCollector->AttributeIsNullified('phone'));
 
-		$oCollector->Collect(1);
+		$oCollector->Collect();
 		$sExpectedCsv = <<<CSV
 primary_key;first_name;name;org_id;phone;mobile_phone;employee_number;email;function
-1;isaac;asimov;Demo;;123456;9998877665544;issac.asimov@function.io;writer
+1;isaac;asimov_null;Demo;;123456;9998877665544;issac.asimov@function.io;writer
+2;isaac;asimov_empty;Demo;;123456;9998877665544;issac.asimov@function.io;writer
+3;isaac;asimov_notempty;Demo;"not empty";123456;9998877665544;issac.asimov@function.io;writer
 
 CSV;
 		$sExpectedNullifiedCsv = <<<CSV
 primary_key;first_name;name;org_id;phone;mobile_phone;employee_number;email;function
-1;isaac;asimov;Demo;<NULL>;123456;9998877665544;issac.asimov@function.io;writer
+1;isaac;asimov_null;Demo;<NULL>;123456;9998877665544;issac.asimov@function.io;writer
+2;isaac;asimov_empty;Demo;<NULL>;123456;9998877665544;issac.asimov@function.io;writer
+3;isaac;asimov_notempty;Demo;"not empty";123456;9998877665544;issac.asimov@function.io;writer
 
 CSV;
 
@@ -158,12 +162,12 @@ public function testUpdateSDSAttributes($aExpectedAttrDef, $aSynchroAttrDef, boo
 	    $oCollector = new iTopPersonCollector();
 	    $oMockClient = $this->CreateMock('RestClient');
 	    $oMockClient->expects($this->exactly($bWillUpdate ? 1 : 0))->method("Update")->willReturn(['code' => 0]);
-	    
+
 	    $bRet = $this->InvokeNonPublicMethod(get_class($oCollector), 'UpdateSDSAttributes', $oCollector, [$aExpectedAttrDef, $aSynchroAttrDef, '', $oMockClient]);
-	   
+
 	    $this->assertTrue($bRet);
 	}
-	
+
 	public function providerUpdateSDSAttributes()
 	{
 	    return [
@@ -271,7 +275,7 @@ public function InvokeNonPublicMethod($sObjectClass, $sMethodName, $oObject, $aA
 	    $class = new \ReflectionClass($sObjectClass);
 	    $method = $class->getMethod($sMethodName);
 	    $method->setAccessible(true);
-	    
+
 	    return $method->invokeArgs($oObject, $aArgs);
 	}
 }
diff --git a/test/collector/attribute_isnullified/iTopPersonCollector.class.inc.php b/test/collector/attribute_isnullified/iTopPersonCollector.class.inc.php
index eb87c65..481ed39 100644
--- a/test/collector/attribute_isnullified/iTopPersonCollector.class.inc.php
+++ b/test/collector/attribute_isnullified/iTopPersonCollector.class.inc.php
@@ -2,29 +2,62 @@
 
 class iTopPersonCollector extends Collector
 {
-	private $bFetched;
+	private $i;
+	private $aCurrentData;
 
 	protected function Fetch()
 	{
-		if (! $this->bFetched) {
-			$this->bFetched = true;
-			return [
-				'primary_key' => 1,
-				'first_name' => "isaac",
-				'name' => "asimov",
-				'org_id' => "Demo",
-				'phone' => null,
-				'mobile_phone' => "123456",
-				'employee_number' => "9998877665544",
-				'email' => "issac.asimov@function.io",
-				'function' => "writer",
-				'Status' => "Active",
+		if (is_null($this->aCurrentData)){
+			$this->i = 0;
+			$this->aCurrentData = [
+				[
+					'primary_key' => 1,
+					'first_name' => "isaac",
+					'name' => "asimov_null",
+					'org_id' => "Demo",
+					'phone' => null,
+					'mobile_phone' => "123456",
+					'employee_number' => "9998877665544",
+					'email' => "issac.asimov@function.io",
+					'function' => "writer",
+					'Status' => "Active",
+				],
+				[
+					'primary_key' => 2,
+					'first_name' => "isaac",
+					'name' => "asimov_empty",
+					'org_id' => "Demo",
+					'phone' => "",
+					'mobile_phone' => "123456",
+					'employee_number' => "9998877665544",
+					'email' => "issac.asimov@function.io",
+					'function' => "writer",
+					'Status' => "Active",
+				],
+				[
+					'primary_key' => 3,
+					'first_name' => "isaac",
+					'name' => "asimov_notempty",
+					'org_id' => "Demo",
+					'phone' => "not empty",
+					'mobile_phone' => "123456",
+					'employee_number' => "9998877665544",
+					'email' => "issac.asimov@function.io",
+					'function' => "writer",
+					'Status' => "Active",
+				],
 			];
 		}
 
-		return null;
+		$res = null;
+		if ($this->i < count($this->aCurrentData)){
+			$res=$this->aCurrentData[$this->i];
+			$this->i++;
+		}
+
+		return $res;
 	}
-	
+
 	/**
 	 * {@inheritDoc}
 	 * @see Collector::AttributeIsOptional()
diff --git a/test/single_json/nullified_json_1/expected_generated.csv b/test/single_json/nullified_json_1/expected_generated.csv
index 3bab6b3..468643d 100644
--- a/test/single_json/nullified_json_1/expected_generated.csv
+++ b/test/single_json/nullified_json_1/expected_generated.csv
@@ -1,4 +1,4 @@
 primary_key;name;status;first_name;email;phone;org_id;function
 1;"My last name";active;"My first name";my.email@foo.org;"+00 000 000 000";1;<NULL>
-2;Picasso;active;Pablo;pablo@demo.com;;3;
-3;Dali;active;Salvador;dali@demo.com;;3;
+2;Picasso;active;Pablo;pablo@demo.com;;3;<NULL>
+3;Dali;active;Salvador;dali@demo.com;;3;<NULL>