diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index 1109c93fad9..eebd5a35c4f 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -5129,6 +5129,13 @@ class Product extends CommonObject
 
 			include_once DOL_DOCUMENT_ROOT.'/product/stock/class/mouvementstock.class.php';
 
+			if ($nbpiece < 0) {
+				if (!$movement) {
+					$movement = 1;
+				}
+				$nbpiece *= -1;
+			}
+
 			$op[0] = "+".trim($nbpiece);
 			$op[1] = "-".trim($nbpiece);
 
@@ -5176,6 +5183,13 @@ class Product extends CommonObject
 
 			include_once DOL_DOCUMENT_ROOT.'/product/stock/class/mouvementstock.class.php';
 
+			if ($nbpiece < 0) {
+				if (!$movement) {
+					$movement = 1;
+				}
+				$nbpiece *= -1;
+			}
+
 			$op[0] = "+".trim($nbpiece);
 			$op[1] = "-".trim($nbpiece);