diff --git a/htdocs/core/class/commonobject.class.php b/htdocs/core/class/commonobject.class.php
index 1ff633f46ce..f2c61bc86a3 100644
--- a/htdocs/core/class/commonobject.class.php
+++ b/htdocs/core/class/commonobject.class.php
@@ -5238,6 +5238,7 @@ abstract class CommonObject
 			   		$mandatorypb = false;
 			   		if ($attributeType == 'link' && $this->array_options[$key] == '-1') $mandatorypb = true;
 			   		if ($this->array_options[$key] === '') $mandatorypb = true;
+					if ($attributeType == 'sellist' && $this->array_options[$key] == '0') $mandatorypb = true;
 			   		if ($mandatorypb)
 			   		{
 			   		    dol_syslog("Mandatory extra field ".$key." is empty");
diff --git a/htdocs/core/class/extrafields.class.php b/htdocs/core/class/extrafields.class.php
index 57e2bf4284a..ed85a328edc 100644
--- a/htdocs/core/class/extrafields.class.php
+++ b/htdocs/core/class/extrafields.class.php
@@ -2060,9 +2060,12 @@ class ExtraFields
 
 				if ($this->attributes[$object->table_element]['required'][$key])	// Value is required
 				{
-					// Check if empty without using GETPOST, value can be alpha, int, array, etc...
+					// check if functionally empty without using GETPOST (depending on the type of extrafield, a
+					// technically non-empty value may be treated as empty functionally).
+					// value can be alpha, int, array, etc...
 				    if ((!is_array($_POST["options_".$key]) && empty($_POST["options_".$key]) && $this->attributes[$object->table_element]['type'][$key] != 'select' && $_POST["options_".$key] != '0')
 				        || (!is_array($_POST["options_".$key]) && empty($_POST["options_".$key]) && $this->attributes[$object->table_element]['type'][$key] == 'select')
+				        || (!is_array($_POST["options_".$key]) && isset($_POST["options_".$key]) && $this->attributes[$object->table_element]['type'][$key] == 'sellist' && $_POST['options_' . $key] == '0')
 						|| (is_array($_POST["options_".$key]) && empty($_POST["options_".$key])))
 					{
 						//print 'ccc'.$value.'-'.$this->attributes[$object->table_element]['required'][$key];