diff --git a/htdocs/product/class/product.class.php b/htdocs/product/class/product.class.php
index 27fb4a4c11c..1999a6f9c4a 100644
--- a/htdocs/product/class/product.class.php
+++ b/htdocs/product/class/product.class.php
@@ -641,18 +641,18 @@ class Product extends CommonObject
 		$this->height = price2num($this->height);
 		$this->height_units = trim($this->height_units);
 		// set unit not defined
-		if (! $this->width_units && $this->length_units) $this->width_units = $this->length_units;    // Not used yet
-		if (! $this->height_units && $this->length_units) $this->height_units = $this->length_units;    // Not used yet
+		if ($this->length_units) $this->width_units = $this->length_units;    // Not used yet
+		if ($this->length_units) $this->height_units = $this->length_units;    // Not used yet
 		// Automated compute surface and volume if not filled
 		if (empty($this->surface) && !empty($this->length) && !empty($this->width) && $this->length_units == $this->width_units)
 		{
 			$this->surface = $this->length * $this->width;
-			$this->surface_units =  $this->width_units;
-			if (empty($this->volume) && !empty($this->height) && $this->length_units == $this->height_units)
-			{
-				$this->volume =  $this->surface * $this->height;
-				$this->volume_units = $this->height_units;
-			}
+			$this->surface_units = $this->length_units + $this->width_units;
+		}
+		if (empty($this->volume) && !empty($this->surface_units) && !empty($this->height) && $this->length_units == $this->height_units)
+		{
+			$this->volume =  $this->surface * $this->height;
+			$this->volume_units = $this->surface_units + $this->height_units;
 		}
 		
 		$this->surface = price2num($this->surface);