diff --git a/htdocs/product/stock/class/mouvementstock.class.php b/htdocs/product/stock/class/mouvementstock.class.php
index 55270e0cd10..c2599faf942 100644
--- a/htdocs/product/stock/class/mouvementstock.class.php
+++ b/htdocs/product/stock/class/mouvementstock.class.php
@@ -475,20 +475,25 @@ class MouvementStock extends CommonObject
 			$newpmp = 0;
 			if (!$error)
 			{
-				// Note: PMP is calculated on stock input only (type of movement = 0 or 3). If type == 0 or 3, qty should be > 0.
-				// Note: Price should always be >0 or 0. PMP should be always >0 (calculated on input)
-				if (($type == 0 || $type == 3) && $price > 0)
+				if ($type == 0 || $type == 3)
 				{
-					$oldqtytouse = ($oldqty >= 0 ? $oldqty : 0);
-					// We make a test on oldpmp>0 to avoid to use normal rule on old data with no pmp field defined
-					if ($oldpmp > 0) $newpmp = price2num((($oldqtytouse * $oldpmp) + ($qty * $price)) / ($oldqtytouse + $qty), 'MU');
-					else
-					{
-						$newpmp = $price; // For this product, PMP was not yet set. We set it to input price.
+					// After a stock increase
+					// Note: PMP is calculated on stock input only (type of movement = 0 or 3). If type == 0 or 3, qty should be > 0.
+					// Note: Price should always be >0 or 0. PMP should be always >0 (calculated on input)
+					if ($price > 0 || (! empty($conf->global->STOCK_UPDATE_AWP_EVEN_WHEN_ENTRY_PRICE_IS_NULL) && $price ==0)) {
+						$oldqtytouse = ($oldqty >= 0 ? $oldqty : 0);
+						// We make a test on oldpmp>0 to avoid to use normal rule on old data with no pmp field defined
+						if ($oldpmp > 0) $newpmp = price2num((($oldqtytouse * $oldpmp) + ($qty * $price)) / ($oldqtytouse + $qty), 'MU');
+						else
+						{
+							$newpmp = $price; // For this product, PMP was not yet set. We set it to input price.
+						}
+						//print "oldqtytouse=".$oldqtytouse." oldpmp=".$oldpmp." oldqtywarehousetouse=".$oldqtywarehousetouse." ";
+						//print "qty=".$qty." newpmp=".$newpmp;
+						//exit;
+					} else {
+						$newpmp = $oldpmp;
 					}
-					//print "oldqtytouse=".$oldqtytouse." oldpmp=".$oldpmp." oldqtywarehousetouse=".$oldqtywarehousetouse." ";
-					//print "qty=".$qty." newpmp=".$newpmp;
-					//exit;
 				}
 				elseif ($type == 1 || $type == 2)
 				{
@@ -497,6 +502,7 @@ class MouvementStock extends CommonObject
 				}
 				else
 				{
+					// Type of movement unknown
 					$newpmp = $oldpmp;
 				}
 			}