diff --git a/product/ERP5/Document/Measure.py b/product/ERP5/Document/Measure.py
index df4e8fb6b27fe0499ba081a121a5b80ca7a9f7b3..7a1f9e1b36dddca48ca68c3192e717286b728407 100644
--- a/product/ERP5/Document/Measure.py
+++ b/product/ERP5/Document/Measure.py
@@ -32,6 +32,13 @@ from Products.ERP5Type.Permissions import AccessContentsInformation
 from Products.ERP5Type.XMLMatrix import XMLMatrix
 from Products.ERP5.Variated import Variated
 
+
+def getQuantity(quantity_unit_value):
+  quantity = quantity_unit_value.getProperty('quantity')
+  if quantity is not None:
+    return float(quantity)
+
+
 class Measure(XMLMatrix):
   """
     A Measure
@@ -132,7 +139,7 @@ class Measure(XMLMatrix):
     metric_type = self.getMetricType()
     if quantity_unit is not None and metric_type and \
         quantity_unit.getParentId() == metric_type.split('/', 1)[0]:
-      return float(quantity_unit.getProperty('quantity'))
+      return getQuantity(quantity_unit)
 
   security.declareProtected(AccessContentsInformation, 'getConvertedQuantity')
   def getConvertedQuantity(self, variation_list=()):
@@ -190,7 +197,7 @@ class Measure(XMLMatrix):
       if quantity is not None:
         quantity *= quantity_unit
         if (not default or quantity ==
-            float(resource.getQuantityUnitValue().getProperty('quantity'))):
+            getQuantity(resource.getQuantityUnitValue())):
           return (uid, resource_uid, '^', metric_type_uid, quantity),
       return ()
 
diff --git a/product/ERP5/Document/Resource.py b/product/ERP5/Document/Resource.py
index 14017d4261329bb58a07e8c1032f6602c7419e3b..b9fd9d6aa6adeb0eb5a93a6d57da179c4ec1b3ad 100644
--- a/product/ERP5/Document/Resource.py
+++ b/product/ERP5/Document/Resource.py
@@ -887,11 +887,11 @@ class Resource(XMLMatrix, Variated):
         # At this point, we know there is no default measure and we must add
         # a row for the management unit, with the resource's uid as uid, and
         # a generic metric_type.
-        quantity = float(quantity_unit_value.getProperty('quantity'))
+        quantity = quantity_unit_value.getProperty('quantity')
         metric_type_uid = self.getPortalObject().portal_categories \
                               .getCategoryUid(metric_type, 'metric_type')
         if quantity and metric_type_uid:
           uid = self.getUid()
-          insert_list += (uid, uid, '^', metric_type_uid, quantity),
+          insert_list += (uid, uid, '^', metric_type_uid, float(quantity)),
 
       return insert_list