diff -r b17dfd0a4fef src/org/openbravo/retail/posterminal/master/BPLocation.java
--- a/src/org/openbravo/retail/posterminal/master/BPLocation.java	Mon Nov 02 11:06:08 2015 +0100
+++ b/src/org/openbravo/retail/posterminal/master/BPLocation.java	Tue Nov 03 18:57:55 2015 +0100
@@ -39,8 +39,8 @@
   @Override
   protected List<String> getQuery(JSONObject jsonsent) throws JSONException {
     Long lastUpdated = jsonsent.has("lastUpdated")
-        && !jsonsent.get("lastUpdated").equals("undefined") ? jsonsent.getLong("lastUpdated")
-        : null;
+        && !jsonsent.get("lastUpdated").equals("undefined")
+        && !jsonsent.get("lastUpdated").equals("null") ? jsonsent.getLong("lastUpdated") : null;
     // if it is a total refresh we need to ensure that all(AND) entities are active. In a
     // incremental refresh, we need to retrieve it if some (OR) ot the entities have changed
     String operator = lastUpdated == null ? " AND " : " OR ";
diff -r b17dfd0a4fef src/org/openbravo/retail/posterminal/master/BusinessPartner.java
--- a/src/org/openbravo/retail/posterminal/master/BusinessPartner.java	Mon Nov 02 11:06:08 2015 +0100
+++ b/src/org/openbravo/retail/posterminal/master/BusinessPartner.java	Tue Nov 03 18:57:55 2015 +0100
@@ -33,8 +33,9 @@
 
   @Override
   protected List<String> getQuery(JSONObject jsonsent) throws JSONException {
-    Long lastUpdated = (jsonsent.has("lastUpdated") && jsonsent.get("lastUpdated") != null && !jsonsent
-        .get("lastUpdated").equals("undefined")) ? jsonsent.getLong("lastUpdated") : null;
+    Long lastUpdated = jsonsent.has("lastUpdated")
+        && !jsonsent.get("lastUpdated").equals("undefined")
+        && !jsonsent.get("lastUpdated").equals("null") ? jsonsent.getLong("lastUpdated") : null;
     // if it is a total refresh we need to ensure that all(AND) entities are active. In a
     // incremental refresh, we need to retrieve it if some (OR) ot the entities have changed
     String operator = lastUpdated == null ? " AND " : " OR ";
diff -r b17dfd0a4fef src/org/openbravo/retail/posterminal/master/Discount.java
--- a/src/org/openbravo/retail/posterminal/master/Discount.java	Mon Nov 02 11:06:08 2015 +0100
+++ b/src/org/openbravo/retail/posterminal/master/Discount.java	Tue Nov 03 18:57:55 2015 +0100
@@ -118,8 +118,8 @@
     today.put("today", value);
     jsonsent.put("parameters", today);
     Long lastUpdated = jsonsent.has("lastUpdated")
-        && !jsonsent.get("lastUpdated").equals("undefined") ? jsonsent.getLong("lastUpdated")
-        : null;
+        && !jsonsent.get("lastUpdated").equals("undefined")
+        && !jsonsent.get("lastUpdated").equals("null") ? jsonsent.getLong("lastUpdated") : null;
     // if it is a total refresh we need to ensure that all(AND) entities are active. In a
     // incremental refresh, we need to retrieve it if some (OR) ot the entities have changed
     jsonsent.put("operator", lastUpdated == null ? " AND " : " OR ");
diff -r b17dfd0a4fef src/org/openbravo/retail/posterminal/master/Product.java
--- a/src/org/openbravo/retail/posterminal/master/Product.java	Mon Nov 02 11:06:08 2015 +0100
+++ b/src/org/openbravo/retail/posterminal/master/Product.java	Tue Nov 03 18:57:55 2015 +0100
@@ -83,8 +83,8 @@
     HQLPropertyList regularProductsHQLProperties = ModelExtensionUtils.getPropertyExtensions(
         extensions, args);
     Long lastUpdated = jsonsent.has("lastUpdated")
-        && !jsonsent.get("lastUpdated").equals("undefined") ? jsonsent.getLong("lastUpdated")
-        : null;
+        && !jsonsent.get("lastUpdated").equals("undefined")
+        && !jsonsent.get("lastUpdated").equals("null") ? jsonsent.getLong("lastUpdated") : null;
     // regular products
     String hql = "select"
         + regularProductsHQLProperties.getHqlSelect()
diff -r b17dfd0a4fef src/org/openbravo/retail/posterminal/master/SalesRepresentative.java
--- a/src/org/openbravo/retail/posterminal/master/SalesRepresentative.java	Mon Nov 02 11:06:08 2015 +0100
+++ b/src/org/openbravo/retail/posterminal/master/SalesRepresentative.java	Tue Nov 03 18:57:55 2015 +0100
@@ -34,8 +34,8 @@
   @Override
   protected List<String> getQuery(JSONObject jsonsent) throws JSONException {
     Long lastUpdated = jsonsent.has("lastUpdated")
-        && !jsonsent.get("lastUpdated").equals("undefined") ? jsonsent.getLong("lastUpdated")
-        : null;
+        && !jsonsent.get("lastUpdated").equals("undefined")
+        && !jsonsent.get("lastUpdated").equals("null") ? jsonsent.getLong("lastUpdated") : null;
     List<String> hqlQueries = new ArrayList<String>();
     HQLPropertyList regularSalesRepresentativeHQLProperties = ModelExtensionUtils
         .getPropertyExtensions(extensions);