diff --git a/fields/__init__.py b/fields/__init__.py
index 1013c35..2d6d386 100644
--- a/fields/__init__.py
+++ b/fields/__init__.py
@@ -61,8 +61,7 @@ class Field:
              value=zobj.getFormattedFieldValue(name, rawValue, showChanges);
              requestValue=zobj.getRequestFieldValue(name);
              inRequest=req.has_key(name);
-             errors=errors|();
-             inError=name in errors;
+             error=req.get('%s_error' % name);
              isMultiple=(field.multiplicity[1] == None) or \
                         (field.multiplicity[1] > 1);
              masterCss=field.slaves and ('master_%s' % name) or '';
@@ -86,8 +85,8 @@ class Field:
      src=":url('help')"/></acronym>''')
 
     # Displays validation-error-related info about a field.
-    pxValidation = Px('''<x><acronym if="inError" title=":errors[name]"><img
-     src=":url('warning')"/></acronym><img if="not inError"
+    pxValidation = Px('''<x><acronym if="error" title=":error"><img
+     src=":url('warning')"/></acronym><img if="not error"
      src=":url('warning_no.gif')"/></x>''')
 
     # Displays the fact that a field is required.
@@ -107,7 +106,7 @@ class Field:
                  layouts, move, indexed, searchable, specificReadPermission,
                  specificWritePermission, width, height, maxChars, colspan,
                  master, masterValue, focus, historized, sync, mapping, label,
-                 sdefault, scolspan, swidth, sheight):
+                 sdefault, scolspan, swidth, sheight, persist):
         # The validator restricts which values may be defined. It can be an
         # interval (1,None), a list of string values ['choice1', 'choice2'],
         # a regular expression, a custom function, a Selection instance, etc.
@@ -215,6 +214,10 @@ class Field:
         # Width and height for the search widget
         self.swidth = swidth or width
         self.sheight = sheight or height
+        # "persist" indicates if field content must be stored in the database.
+        # For some fields it is not wanted (ie, fields used only as masters to
+        # update slave's selectable values).
+        self.persist = persist
 
     def init(self, name, klass, appName):
         '''When the application server starts, this secondary constructor is
@@ -584,26 +587,14 @@ class Field:
             res += '+'
         return res
 
-    def getOnChange(self, name, zobj, layoutType):
+    def getOnChange(self, zobj, layoutType):
         '''When this field is a master, this method computes the call to the
            Javascript function that will be called when its value changes (in
            order to update slaves).'''
         if not self.slaves: return ''
         q = zobj.getTool().quote
-        # Create the dict of request values for slave fields.
-        rvs = {}
-        req = zobj.REQUEST
-        for slave in self.slaves:
-            name = slave.name
-            if not req.has_key(name): continue
-            if not req[name]: continue
-            rvs[name] = req[name]
-        if rvs:
-            rvs = ',%s' % sutils.getStringDict(rvs)
-        else:
-            rvs = ''
-        return 'updateSlaves(this,null,%s,%s%s)' % \
-               (q(zobj.absolute_url()), q(layoutType), rvs)
+        return 'updateSlaves(this,null,%s,%s)' % \
+               (q(zobj.absolute_url()), q(layoutType))
 
     def isEmptyValue(self, value, obj=None):
         '''Returns True if the p_value must be considered as an empty value.'''
@@ -680,7 +671,7 @@ class Field:
     def store(self, obj, value):
         '''Stores the p_value (produced by m_getStorableValue) that complies to
            p_self type definition on p_obj.'''
-        setattr(obj, self.name, value)
+        if self.persist: setattr(obj, self.name, value)
 
     def callMethod(self, obj, method, cache=True):
         '''This method is used to call a p_method on p_obj. p_method is part of
diff --git a/fields/action.py b/fields/action.py
index 1abf0ac..36ab937 100644
--- a/fields/action.py
+++ b/fields/action.py
@@ -74,7 +74,7 @@ class Action(Field):
                        move, indexed, False, specificReadPermission,
                        specificWritePermission, width, height, None, colspan,
                        master, masterValue, focus, historized, False, mapping,
-                       label, None, None, None, None)
+                       label, None, None, None, None, False)
         self.validable = False
 
     def getDefaultLayouts(self): return {'view': 'l-f', 'edit': 'lrv-f'}
diff --git a/fields/boolean.py b/fields/boolean.py
index 0e2ca11..e283d96 100644
--- a/fields/boolean.py
+++ b/fields/boolean.py
@@ -23,19 +23,17 @@ from appy.gen.layout import Table
 class Boolean(Field):
     '''Field for storing boolean values.'''
 
-    pxView = pxCell = Px('''
-     <x><x>:value</x>
-      <input type="hidden" if="masterCss"
-             class=":masterCss" value=":rawValue" name=":name" id=":name"/>
-     </x>''')
+    pxView = pxCell = Px('''<x>:value</x>
+     <input type="hidden" if="masterCss"
+            class=":masterCss" value=":rawValue" name=":name" id=":name"/>''')
 
     pxEdit = Px('''
      <x var="isChecked=field.isChecked(zobj, rawValue)">
       <input type="checkbox" name=":name + '_visible'" id=":name"
              class=":masterCss" checked=":isChecked"
              onclick=":'toggleCheckbox(%s, %s); %s' % (q(name), \
-                       q('%s_hidden' % name), field.getOnChange(name, zobj, \
-                       layoutType))"/>
+                       q('%s_hidden' % name), \
+                       field.getOnChange(zobj, layoutType))"/>
       <input type="hidden" name=":name" id=":'%s_hidden' % name"
              value=":isChecked and 'True' or 'False'"/>
      </x>''')
@@ -64,13 +62,14 @@ class Boolean(Field):
                  specificWritePermission=False, width=None, height=None,
                  maxChars=None, colspan=1, master=None, masterValue=None,
                  focus=False, historized=False, mapping=None, label=None,
-                 sdefault=False, scolspan=1, swidth=None, sheight=None):
+                 sdefault=False, scolspan=1, swidth=None, sheight=None,
+                 persist=True):
         Field.__init__(self, validator, multiplicity, default, show, page,
                        group, layouts, move, indexed, searchable,
                        specificReadPermission, specificWritePermission, width,
                        height, None, colspan, master, masterValue, focus,
                        historized, True, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, persist)
         self.pythonType = bool
 
     # Layout including a description
diff --git a/fields/calendar.py b/fields/calendar.py
index c54c82c..f5b684e 100644
--- a/fields/calendar.py
+++ b/fields/calendar.py
@@ -222,7 +222,7 @@ class Calendar(Field):
                        layouts, move, False, False, specificReadPermission,
                        specificWritePermission, width, height, None, colspan,
                        master, masterValue, focus, False, True, mapping, label,
-                       None, None, None, None)
+                       None, None, None, None, True)
         # eventTypes can be a "static" list or tuple of strings that identify
         # the types of events that are supported by this calendar. It can also
         # be a method that computes such a "dynamic" list or tuple. When
diff --git a/fields/computed.py b/fields/computed.py
index 1a64a1d..ea1a6b3 100644
--- a/fields/computed.py
+++ b/fields/computed.py
@@ -70,7 +70,7 @@ class Computed(Field):
                        specificReadPermission, specificWritePermission, width,
                        height, None, colspan, master, masterValue, focus,
                        historized, sync, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, False)
         self.validable = False
 
     def getValue(self, obj):
diff --git a/fields/date.py b/fields/date.py
index 4f2416f..c266e93 100644
--- a/fields/date.py
+++ b/fields/date.py
@@ -173,7 +173,8 @@ class Date(Field):
                  specificWritePermission=False, width=None, height=None,
                  maxChars=None, colspan=1, master=None, masterValue=None,
                  focus=False, historized=False, mapping=None, label=None,
-                 sdefault=None, scolspan=1, swidth=None, sheight=None):
+                 sdefault=None, scolspan=1, swidth=None, sheight=None,
+                 persist=True):
         self.format = format
         self.calendar = calendar
         self.startYear = startYear
@@ -186,7 +187,7 @@ class Date(Field):
                        specificReadPermission, specificWritePermission, width,
                        height, None, colspan, master, masterValue, focus,
                        historized, True, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, persist)
 
     def getCss(self, layoutType, res):
         # CSS files are only required if the calendar must be shown.
diff --git a/fields/file.py b/fields/file.py
index 877ccff..fd0ba2c 100644
--- a/fields/file.py
+++ b/fields/file.py
@@ -279,7 +279,7 @@ class File(Field):
                        specificReadPermission, specificWritePermission, width,
                        height, None, colspan, master, masterValue, focus,
                        historized, True, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, True)
 
     @staticmethod
     def getFileObject(filePath, fileName=None, zope=False):
diff --git a/fields/float.py b/fields/float.py
index 4ce633a..c0d69fe 100644
--- a/fields/float.py
+++ b/fields/float.py
@@ -58,7 +58,7 @@ class Float(Field):
                  maxChars=13, colspan=1, master=None, masterValue=None,
                  focus=False, historized=False, mapping=None, label=None,
                  sdefault=('',''), scolspan=1, swidth=None, sheight=None,
-                 precision=None, sep=(',', '.'), tsep=' '):
+                 persist=True, precision=None, sep=(',', '.'), tsep=' '):
         # The precision is the number of decimal digits. This number is used
         # for rendering the float, but the internal float representation is not
         # rounded.
@@ -80,7 +80,7 @@ class Float(Field):
                        specificReadPermission, specificWritePermission, width,
                        height, maxChars, colspan, master, masterValue, focus,
                        historized, True, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, persist)
         self.pythonType = float
 
     def getFormattedValue(self, obj, value, showChanges=False):
diff --git a/fields/info.py b/fields/info.py
index 527d305..94a9e35 100644
--- a/fields/info.py
+++ b/fields/info.py
@@ -34,6 +34,6 @@ class Info(Field):
                        move, indexed, False, specificReadPermission,
                        specificWritePermission, width, height, None, colspan,
                        master, masterValue, focus, historized, False, mapping,
-                       label, None, None, None, None)
+                       label, None, None, None, None, False)
         self.validable = False
 # ------------------------------------------------------------------------------
diff --git a/fields/integer.py b/fields/integer.py
index 009fe40..76e8823 100644
--- a/fields/integer.py
+++ b/fields/integer.py
@@ -54,13 +54,14 @@ class Integer(Field):
                  specificWritePermission=False, width=5, height=None,
                  maxChars=13, colspan=1, master=None, masterValue=None,
                  focus=False, historized=False, mapping=None, label=None,
-                 sdefault=('',''), scolspan=1, swidth=None, sheight=None):
+                 sdefault=('',''), scolspan=1, swidth=None, sheight=None,
+                 persist=True):
         Field.__init__(self, validator, multiplicity, default, show, page,
                        group, layouts, move, indexed, searchable,
                        specificReadPermission, specificWritePermission, width,
                        height, maxChars, colspan, master, masterValue, focus,
                        historized, True, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, persist)
         self.pythonType = long
 
     def validateValue(self, obj, value):
diff --git a/fields/list.py b/fields/list.py
index e062e1f..b69e953 100644
--- a/fields/list.py
+++ b/fields/list.py
@@ -83,7 +83,8 @@ class List(Field):
                        group, layouts, move, indexed, False,
                        specificReadPermission, specificWritePermission, width,
                        height, None, colspan, master, masterValue, focus,
-                       historized, True, mapping, label, None, None, None, None)
+                       historized, True, mapping, label, None, None, None, None,
+                       True)
         self.validable = True
         # Tuples of (names, Field instances) determining the format of every
         # element in the list.
diff --git a/fields/ogone.py b/fields/ogone.py
index 269accc..3e69e84 100644
--- a/fields/ogone.py
+++ b/fields/ogone.py
@@ -54,7 +54,7 @@ class Ogone(Field):
                        move, False, False,specificReadPermission,
                        specificWritePermission, width, height, None, colspan,
                        master, masterValue, focus, False, True, mapping, label,
-                       None, None, None, None)
+                       None, None, None, None, False)
         # orderMethod must contain a method returning a dict containing info
         # about the order. Following keys are mandatory:
         #   * orderID   An identifier for the order. Don't use the object UID
diff --git a/fields/pod.py b/fields/pod.py
index eba7c1c..41faed4 100644
--- a/fields/pod.py
+++ b/fields/pod.py
@@ -84,7 +84,9 @@ class Pod(Field):
                        move, indexed, searchable, specificReadPermission,
                        specificWritePermission, width, height, None, colspan,
                        master, masterValue, focus, historized, False, mapping,
-                       label, None, None, None, None)
+                       label, None, None, None, None, True)
+        # Param "persist" is set to True but actually, persistence for a pod
+        # field is determined by freezing.
         self.validable = False
 
     def isFrozen(self, obj):
diff --git a/fields/ref.py b/fields/ref.py
index f6b1bfe..50d1858 100644
--- a/fields/ref.py
+++ b/fields/ref.py
@@ -286,7 +286,7 @@ class Ref(Field):
                    uids=[o.UID() for o in \
                          field.getLinkedObjects(zobj).objects]"
              name=":name" id=":name" size=":isMultiple and field.height or ''"
-             onchange=":field.getOnChange(name, zobj, layoutType)"
+             onchange=":field.getOnChange(zobj, layoutType)"
              multiple=":isMultiple">
       <option value="" if="not isMultiple">:_('choose_a_value')</option>
       <option for="ztied in zobjects" var2="uid=ztied.o.UID()"
@@ -328,8 +328,8 @@ class Ref(Field):
                  label=None, queryable=False, queryFields=None, queryNbCols=1,
                  navigable=False, searchSelect=None, changeOrder=True,
                  sdefault='', scolspan=1, swidth=None, sheight=None,
-                 render='list', menuIdMethod=None, menuInfoMethod=None,
-                 menuUrlMethod=None):
+                 persist=True, render='list', menuIdMethod=None,
+                 menuInfoMethod=None, menuUrlMethod=None):
         self.klass = klass
         self.attribute = attribute
         # May the user add new objects through this ref ?
@@ -431,7 +431,7 @@ class Ref(Field):
                        specificReadPermission, specificWritePermission, width,
                        height, None, colspan, master, masterValue, focus,
                        historized, sync, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, persist)
         self.validable = self.link
 
     def getDefaultLayouts(self):
@@ -662,6 +662,7 @@ class Ref(Field):
            * a Zope object;
            * a Appy object;
            * a list of Appy or Zope objects.'''
+        if not self.persist: return
         # Standardize p_value into a list of Zope objects
         objects = value
         if not objects: objects = []
@@ -759,6 +760,11 @@ class Ref(Field):
             res = self.masterValue(obj, masterValues)
             return res
         else:
+            # If this field is a ajax-updatable slave, no need to compute
+            # selectable objects: it will be overridden by method
+            # self.masterValue by a subsequent ajax request (=the "if" statement
+            # above).
+            if self.masterValue and callable(self.masterValue): return []
             if not self.select:
                 # No select method has been defined: we must retrieve all
                 # objects of the referred type that the user is allowed to
diff --git a/fields/string.py b/fields/string.py
index 0c45e16..3ff6d25 100644
--- a/fields/string.py
+++ b/fields/string.py
@@ -110,7 +110,7 @@ class String(Field):
                       withTranslations=True, withBlankValue=True)"
               name=":name" id=":name" class=":masterCss"
               multiple=":isMultiple and 'multiple' or ''"
-              onchange=":field.getOnChange(name, zobj, layoutType)"
+              onchange=":field.getOnChange(zobj, layoutType)"
               size=":isMultiple and field.height or 1">
        <option for="val in possibleValues" value=":val[0]"
                selected=":field.isSelected(zobj, name, val[0], rawValue)"
@@ -292,8 +292,9 @@ class String(Field):
                  width=None, height=None, maxChars=None, colspan=1, master=None,
                  masterValue=None, focus=False, historized=False, mapping=None,
                  label=None, sdefault='', scolspan=1, swidth=None, sheight=None,
-                 transform='none', styles=('p','h1','h2','h3','h4'),
-                 allowImageUpload=True, inlineEdit=False):
+                 persist=True, transform='none',
+                 styles=('p','h1','h2','h3','h4'), allowImageUpload=True,
+                 inlineEdit=False):
         # According to format, the widget will be different: input field,
         # textarea, inline editor... Note that there can be only one String
         # field of format CAPTCHA by page, because the captcha challenge is
@@ -318,7 +319,7 @@ class String(Field):
                        specificReadPermission, specificWritePermission, width,
                        height, maxChars, colspan, master, masterValue, focus,
                        historized, True, mapping, label, sdefault, scolspan,
-                       swidth, sheight)
+                       swidth, sheight, persist)
         self.isSelect = self.isSelection()
         # If self.isSelect, self.sdefault must be a list of value(s).
         if self.isSelect and not sdefault:
@@ -390,6 +391,7 @@ class String(Field):
 
     def store(self, obj, value):
         '''When the value is XHTML, we perform some cleanup.'''
+        if not self.persist: return
         if (self.format == String.XHTML) and value:
             # When image upload is allowed, ckeditor inserts some "style" attrs
             # (ie for image size when images are resized). So in this case we
diff --git a/gen/mixins/__init__.py b/gen/mixins/__init__.py
index eaf311f..43d93b3 100644
--- a/gen/mixins/__init__.py
+++ b/gen/mixins/__init__.py
@@ -417,7 +417,7 @@ class BaseMixin:
         # Trigger field-specific validation
         self.intraFieldValidation(errors, values)
         if errors.__dict__:
-            rq.set('errors', errors.__dict__)
+            for k,v in errors.__dict__.iteritems(): rq.set('%s_error' % k, v)
             self.say(errorMessage)
             return self.gotoEdit()
 
@@ -425,7 +425,7 @@ class BaseMixin:
         msg = self.interFieldValidation(errors, values)
         if not msg: msg = errorMessage
         if errors.__dict__:
-            rq.set('errors', errors.__dict__)
+            for k,v in errors.__dict__.iteritems(): rq.set('%s_error' % k, v)
             self.say(msg)
             return self.gotoEdit()
 
@@ -814,19 +814,27 @@ class BaseMixin:
             res.append(field)
         return res
 
-    def getSlaveFieldsRequestValues(self, pageName):
-        '''Returns the list of slave fields having a masterValue being a
-           method.'''
-        res = {}
+    def getSlavesRequestInfo(self, pageName):
+        '''When slave fields must be updated via Ajax requests, we must carry
+           some information from the global request object to the ajax requests:
+           - the selected values in slave fields;
+           - validation errors.'''
+        requestValues = {}
+        errors = {}
         req = self.REQUEST
         for field in self.getAllAppyTypes():
             if field.page.name != pageName: continue
             if field.masterValue and callable(field.masterValue):
-                # We have such a field
+                # We have a slave field that is updated via ajax requests.
                 name = field.name
+                # Remember the request value for this field if present.
                 if req.has_key(name) and req[name]:
-                    res[name] = req[name]
-        return sutils.getStringDict(res)
+                    requestValues[name] = req[name]
+                # Remember the validation error for this field if present.
+                errorKey = '%s_error' % name
+                if req.has_key(errorKey):
+                    errors[name] = req[errorKey]
+        return sutils.getStringDict(requestValues), sutils.getStringDict(errors)
 
     def getCssJs(self, fields, layoutType, res):
         '''Gets, in p_res ~{'css':[s_css], 'js':[s_js]}~ the lists of
diff --git a/gen/ui/appy.js b/gen/ui/appy.js
index f9298ce..1b9071e 100644
--- a/gen/ui/appy.js
+++ b/gen/ui/appy.js
@@ -83,6 +83,20 @@ function evalInnerScripts(xhrObject, hookElem) {
   for (var i=0; i<scripts.length; i++) { eval(scripts[i].innerHTML) }
 }
 
+function injectChunk(elem, content){
+  if (!isIe) elem.innerHTML = content;
+  else {
+    if (elem.tagName != 'TABLE') elem.innerHTML = content;
+    else {
+      /* IE doesn't want to replace content of a table. Force it to do so via
+         a temporary DOM element. */
+      var temp = document.createElement('div');
+      temp.innerHTML = content;
+      elem.replaceChild(temp.firstChild, elem.firstChild);
+    }
+  }
+}
+
 function getAjaxChunk(pos) {
   // This function is the callback called by the AJAX machinery (see function
   // askAjaxChunk below) when an Ajax response is available.
@@ -93,13 +107,14 @@ function getAjaxChunk(pos) {
     if (xhrObjects[pos].xhr.readyState == 1) {
       // The request has been initialized: display the waiting radar
       var hookElem = document.getElementById(hook);
-      if (hookElem) hookElem.innerHTML = "<div align=\"center\"><img src=\"ui/waiting.gif\"/><\/div>";
+      if (hookElem)
+        injectChunk(hookElem, "<div align=\"center\"><img src=\"ui/waiting.gif\"/><\/div>");
     }
     if (xhrObjects[pos].xhr.readyState == 4) {
       // We have received the HTML chunk
       var hookElem = document.getElementById(hook);
       if (hookElem && (xhrObjects[pos].xhr.status == 200)) {
-        hookElem.innerHTML = xhrObjects[pos].xhr.responseText;
+        injectChunk(hookElem, xhrObjects[pos].xhr.responseText);
         // Call a custom Javascript function if required
         if (xhrObjects[pos].onGet) {
           xhrObjects[pos].onGet(xhrObjects[pos], hookElem);
@@ -229,12 +244,13 @@ function askComputedField(hookId, objectUrl, fieldName) {
 }
 
 function askField(hookId, objectUrl, layoutType, showChanges, masterValues,
-                  requestValue){
+                  requestValue, error){
   // Sends an Ajax request for getting the content of any field.
   var fieldName = hookId.split('_')[1];
   var params = {'layoutType': layoutType, 'showChanges': showChanges};
   if (masterValues) params['masterValues'] = masterValues.join('*');
   if (requestValue) params[fieldName] = requestValue;
+  if (error) params[fieldName + '_error'] = error;
   askAjaxChunk(hookId, 'GET', objectUrl, fieldName+':pxRender', params, null,
                evalInnerScripts);
 }
@@ -354,7 +370,7 @@ function getSlaves(master) {
   return res;
 }
 
-function updateSlaves(master, slave, objectUrl, layoutType, requestValues){
+function updateSlaves(master,slave,objectUrl,layoutType,requestValues,errors){
   /* Given the value(s) in a master field, we must update slave's visibility or
      value(s). If p_slave is given, it updates only this slave. Else, it updates
      all slaves of p_master. */
@@ -382,15 +398,19 @@ function updateSlaves(master, slave, objectUrl, layoutType, requestValues){
       var reqValue = null;
       if (requestValues && (slaveName in requestValues))
         reqValue = requestValues[slaveName];
-      askField(slaveId, objectUrl, layoutType, false, masterValues, reqValue);
+      var err = null;
+      if (errors && (slaveName in errors))
+        err = errors[slaveName];
+      askField(slaveId,objectUrl,layoutType,false,masterValues,reqValue,err);
     }
   }
 }
 
-function initSlaves(objectUrl, layoutType, requestValues) {
+function initSlaves(objectUrl, layoutType, requestValues, errors) {
   /* When the current page is loaded, we must set the correct state for all
-     slave fields. p_requestValues are those from the slave fields that must
-     be ajax-updated. */
+     slave fields. For those that are updated via Ajax requests, their
+     p_requestValues and validation p_errors must be carried to those
+     requests. */
   slaves = getElementsHavingName('table', 'slave');
   i = slaves.length -1;
   while (i >= 0) {
@@ -398,8 +418,7 @@ function initSlaves(objectUrl, layoutType, requestValues) {
     master = document.getElementById(masterName);
     // If master is not here, we can't hide its slaves when appropriate.
     if (master) {
-      updateSlaves(master, slaves[i], objectUrl, layoutType, requestValues);
-    }
+      updateSlaves(master,slaves[i],objectUrl,layoutType,requestValues,errors);}
     i -= 1;
   }
 }
diff --git a/gen/wrappers/ToolWrapper.py b/gen/wrappers/ToolWrapper.py
index 40e40f7..c5b1a4b 100644
--- a/gen/wrappers/ToolWrapper.py
+++ b/gen/wrappers/ToolWrapper.py
@@ -141,9 +141,10 @@ class ToolWrapper(AbstractWrapper):
     </x>''')
 
     pxPageBottom = Px('''
-     <script type="text/javascript">:'initSlaves(%s,%s,%s)' % \
-                    (q(zobj.absolute_url()), q(layoutType), \
-                     zobj.getSlaveFieldsRequestValues(page))</script>''')
+     <script var="info=zobj.getSlavesRequestInfo(page)"
+             type="text/javascript">:'initSlaves(%s,%s,%s,%s)' % \
+                    (q(zobj.absolute_url()), q(layoutType), info[0], info[1])
+     </script>''')
 
     pxPortlet = Px('''
      <x var="toolUrl=tool.url;
diff --git a/gen/wrappers/__init__.py b/gen/wrappers/__init__.py
index 02e142b..79e8f07 100644
--- a/gen/wrappers/__init__.py
+++ b/gen/wrappers/__init__.py
@@ -533,7 +533,7 @@ class AbstractWrapper(object):
 
     pxEdit = Px('''
      <x var="x=zobj.allows('write', raiseError=True);
-             errors=req.get('errors', None) or {};
+             errors=req.get('errors', {});
              layout=zobj.getPageLayout(layoutType);
              cssJs={};
              phaseObj=zobj.getAppyPhases(currentOnly=True, \