diff --git a/htdocs/install/mysql/migration/12.0.0-13.0.0.sql b/htdocs/install/mysql/migration/12.0.0-13.0.0.sql
index bf9432a6e81..f370863004a 100644
--- a/htdocs/install/mysql/migration/12.0.0-13.0.0.sql
+++ b/htdocs/install/mysql/migration/12.0.0-13.0.0.sql
@@ -408,13 +408,16 @@ DELETE FROM llx_rights_def where module = 'holiday' and perms = 'lire_tous';
 
 CREATE TABLE llx_c_product_nature (
       rowid integer AUTO_INCREMENT PRIMARY KEY,
-      code integer NOT NULL,
+      code tinyint NOT NULL,
       label varchar(100),
       active tinyint DEFAULT 1  NOT NULL
 ) ENGINE=innodb;
 
 ALTER TABLE llx_c_product_nature ADD UNIQUE INDEX uk_c_product_nature(code);
 
-INSERT INTO llx_c_product_nature (code, label, active) VALUES (-1, '', 1);
 INSERT INTO llx_c_product_nature (code, label, active) VALUES (0, 'RowMaterial', 1);
 INSERT INTO llx_c_product_nature (code, label, active) VALUES (1, 'Finished', 1);
+
+ALTER TABLE llx_product MODIFY COLUMN finished tinyint DEFAULT NULL;
+ALTER TABLE llx_product ADD CONSTRAINT fk_product_finished FOREIGN KEY (finished) REFERENCES llx_c_product_nature (code);
+
diff --git a/htdocs/install/mysql/tables/llx_c_product_nature.sql b/htdocs/install/mysql/tables/llx_c_product_nature.sql
index b2f9892aa1e..3c467ce7cf8 100644
--- a/htdocs/install/mysql/tables/llx_c_product_nature.sql
+++ b/htdocs/install/mysql/tables/llx_c_product_nature.sql
@@ -18,7 +18,7 @@
 
 CREATE TABLE llx_c_product_nature (
      rowid integer AUTO_INCREMENT PRIMARY KEY,
-     code varchar(3) NOT NULL,
+     code tinyint NOT NULL,
      label varchar(100),
      active tinyint DEFAULT 1  NOT NULL
 ) ENGINE=innodb;
diff --git a/htdocs/install/mysql/tables/llx_product.key.sql b/htdocs/install/mysql/tables/llx_product.key.sql
index c3dd33c88c5..c0526a8f2cc 100644
--- a/htdocs/install/mysql/tables/llx_product.key.sql
+++ b/htdocs/install/mysql/tables/llx_product.key.sql
@@ -33,6 +33,7 @@ ALTER TABLE llx_product ADD INDEX idx_product_fk_barcode_type (fk_barcode_type);
 ALTER TABLE llx_product ADD INDEX idx_product_fk_project (fk_project);
 ALTER TABLE llx_product ADD UNIQUE INDEX uk_product_barcode (barcode, fk_barcode_type, entity);
 ALTER TABLE llx_product ADD CONSTRAINT fk_product_fk_unit FOREIGN KEY (fk_unit) REFERENCES llx_c_units (rowid);
+ALTER TABLE llx_product ADD CONSTRAINT fk_product_finished FOREIGN KEY (finished) REFERENCES llx_c_product_nature (code);
 
 ALTER TABLE  llx_product ADD CONSTRAINT fk_product_fk_country FOREIGN KEY (fk_country) REFERENCES  llx_c_country (rowid);
 ALTER TABLE  llx_product ADD CONSTRAINT fk_product_barcode_type FOREIGN KEY (fk_barcode_type) REFERENCES  llx_c_barcode_type (rowid);
diff --git a/htdocs/install/mysql/tables/llx_product.sql b/htdocs/install/mysql/tables/llx_product.sql
index bc583a76ce2..2431c884c62 100644
--- a/htdocs/install/mysql/tables/llx_product.sql
+++ b/htdocs/install/mysql/tables/llx_product.sql
@@ -92,7 +92,7 @@ create table llx_product
   lifo                          double(24,8),                       -- To store valuation of stock calculated using lifo method, for this product. TODO Not used, should be replaced by stock value stored into movement table.
   fk_default_warehouse          integer      DEFAULT NULL,
   canvas                        varchar(32)  DEFAULT NULL,
-  finished                      tinyint      DEFAULT NULL,          -- 1=manufactured product, 0=matiere premiere
+  finished                      tinyint      DEFAULT NULL,          -- see dictionnary c_product_nature
   hidden                        tinyint      DEFAULT 0,             -- Not used. Deprecated.
   import_key                    varchar(14),                        -- Import key
   model_pdf                     varchar(255),                       -- model save dodument used
diff --git a/htdocs/product/card.php b/htdocs/product/card.php
index e3467e871c8..62813ee2a57 100644
--- a/htdocs/product/card.php
+++ b/htdocs/product/card.php
@@ -321,8 +321,19 @@ if (empty($reshook))
 			$object->surface_units      	 = GETPOST('surface_units'); // This is not the fk_unit but the power of unit
 			$object->volume             	 = GETPOST('volume');
 			$object->volume_units       	 = GETPOST('volume_units'); // This is not the fk_unit but the power of unit
-			$object->finished           	 = GETPOST('finished', 'alpha');
-			$object->fk_unit = GETPOST('units', 'alpha'); // This is the fk_unit of sale
+			$finished               = GETPOST('finished', 'int');
+			if ($finished > 0) {
+				$object->finished = $finished;
+			} else {
+				$object->finished = null;
+			}
+
+			$units = GETPOST('units', 'int');
+			if ($units > 0) {
+				$object->fk_unit = $units;
+			} else {
+				$object->fk_unit = null;
+			}
 
 			$accountancy_code_sell = GETPOST('accountancy_code_sell', 'alpha');
 			$accountancy_code_sell_intra = GETPOST('accountancy_code_sell_intra', 'alpha');
@@ -435,10 +446,15 @@ if (empty($reshook))
 				$object->surface_units          = GETPOST('surface_units'); // This is not the fk_unit but the power of unit
 				$object->volume                 = GETPOST('volume');
 				$object->volume_units           = GETPOST('volume_units'); // This is not the fk_unit but the power of unit
-				$object->finished               = GETPOST('finished', 'alpha');
+
+				$finished               = GETPOST('finished', 'int');
+				if ($finished >= 0) {
+					$object->finished = $finished;
+				} else {
+					$object->finished = null;
+				}
 
 				$units = GETPOST('units', 'int');
-
 				if ($units > 0) {
 					$object->fk_unit = $units;
 				} else {
@@ -1547,8 +1563,7 @@ if (is_object($objcanvas) && $objcanvas->displayCanvasExists($action))
 			} else {
 				// Nature
 				print '<tr><td>'.$form->textwithpicto($langs->trans("NatureOfProductShort"), $langs->trans("NatureOfProductDesc")).'</td><td colspan="3">';
-				$statutarray = array('-1'=>'&nbsp;', '1' => $langs->trans("Finished"), '0' => $langs->trans("RowMaterial"));
-				print $form->selectarray('finished', $statutarray, $object->finished);
+				print $formproduct->selectProductNature('finished', $object->finished);
 				print '</td></tr>';
 
 				// Brut Weight
diff --git a/htdocs/product/class/html.formproduct.class.php b/htdocs/product/class/html.formproduct.class.php
index fa1b349ef5c..8241be3446e 100644
--- a/htdocs/product/class/html.formproduct.class.php
+++ b/htdocs/product/class/html.formproduct.class.php
@@ -430,14 +430,16 @@ class FormProduct
 	 *  NAture of product labels are defined in llx_c_product_nature
 	 *
 	 *  @param  string		$name                Name of HTML field
-	 *  @param  string		$default             Preselected value
-	 *  @param  int         $mode                1=Use label as value, 0=Use rowid
+	 *  @param  string		$selected             Preselected value
+	 *  @param  int         $mode                1=Use label as value, 0=Use code
 	 *  @return string
 	 */
-	public function selectProductNature($name = 'finished', $default = '-1', $mode = 0)
+	public function selectProductNature($name = 'finished', $selected = '', $mode = 0)
 	{
 		global $langs, $db;
 
+		$langs->load('products');
+
 		$return = '';
 
 		// TODO Use a cache
@@ -459,18 +461,29 @@ class FormProduct
 			return -1;
 		} else {
 			$return .= '<select class="flat" name="'.$name.'">';
+			$return .= '<option value="-1"';
+			if ($selected=='' || $selected=='-1') {
+				$return .= ' selected';
+			}
+			$return .= '></option>';
+			if (!empty($productNature->records) && is_array($productNature->records)) {
+				foreach ($productNature->records as $lines) {
+					$return .= '<option value="';
+					if ($mode == 1) $return .= $lines->label;
+					else $return .= $lines->code;
 
-			foreach ($productNature->records as $lines)
-			{
-				$return .= '<option value="';
-				if ($mode == 1) $return .= $lines->label;
-				else $return .= $lines->id;
-				$return .= '"';
-				if ($mode == 1 && $lines->label == $default) $return .= ' selected';
-				elseif ($mode == 0 && $lines->code == $default) $return .= ' selected';
-				$return .= '>';
-				else $return .= $langs->trans($lines->label);
-				$return .= '</option>';
+					$return .= '"';
+
+					if ($mode == 1 && $lines->label == $selected) {
+						$return .= ' selected';
+					} elseif ($lines->code == $selected) {
+						$return .= ' selected';
+					}
+
+					$return .= '>';
+					$return .= $langs->trans($lines->label);
+					$return .= '</option>';
+				}
 			}
 			$return .= '</select>';
 		}
diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index 18565347072..edaa5e6857b 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -983,7 +983,7 @@ class Product extends CommonObject
 			$sql .= ", tosell = ".(int) $this->status;
 			$sql .= ", tobuy = ".(int) $this->status_buy;
 			$sql .= ", tobatch = ".((empty($this->status_batch) || $this->status_batch < 0) ? '0' : (int) $this->status_batch);
-			$sql .= ", finished = ".((!isset($this->finished) || $this->finished < 0) ? "null" : (int) $this->finished);
+			$sql .= ", finished = ".((!isset($this->finished) || $this->finished < 0 || $this->finished == '') ? "null" : (int) $this->finished);
 			$sql .= ", net_measure = ".($this->net_measure != '' ? "'".$this->db->escape($this->net_measure)."'" : 'null');
 			$sql .= ", net_measure_units = ".($this->net_measure_units != '' ? "'".$this->db->escape($this->net_measure_units)."'" : 'null');
 			$sql .= ", weight = ".($this->weight != '' ? "'".$this->db->escape($this->weight)."'" : 'null');
@@ -4562,10 +4562,21 @@ class Product extends CommonObject
 		global $langs;
 		$langs->load('products');
 
-		if ($this->finished == '0') { return $langs->trans("RowMaterial");
-		}
-		if ($this->finished == '1') { return $langs->trans("Finished");
+		if (isset($this->finished) && $this->finished>=0) {
+			$sql = 'SELECT label, code FROM '.MAIN_DB_PREFIX.'c_product_nature where code='.$this->finished.' AND active=1';
+			$resql = $this->db->query($sql);
+			if ($resql && $this->db->num_rows($resql) > 0) {
+				$res = $this->db->fetch_array($resql);
+				$label = $langs->trans($res['label']);
+				$this->db->free($resql);
+				return $label;
+			} else {
+				$this->error = $this->db->error().' sql='.$sql;
+				dol_syslog(get_class($this)."::".__METHOD__.' Error '.$this->error, LOG_ERR);
+				return -1;
+			}
 		}
+
 		return '';
 	}