diff --git a/product/ERP5Form/ProxyField.py b/product/ERP5Form/ProxyField.py
index ea0ef6d3d5409d4ebacd3680deeee310293dd0d3..5bf88f6d13223383f42e991613b15416fd473774 100644
--- a/product/ERP5Form/ProxyField.py
+++ b/product/ERP5Form/ProxyField.py
@@ -441,11 +441,12 @@ class ProxyField(ZMIField):
       template_field = field.getTemplateField()
       if template_field.__class__ != ProxyField:
         break
-      if aq_base(template_field) in chain:
+      template_field_base = aq_base(template_field)
+      if template_field_base in chain:
         LOG('ProxyField', WARNING, 'Infinite loop detected in %s.' %
             '/'.join(self.getPhysicalPath()))
         return
-      chain.append(aq_base(template_field))
+      chain.append(template_field_base)
       field = template_field
     return template_field
 
@@ -691,9 +692,11 @@ class ProxyField(ZMIField):
     getTransactionalVariable(self)[self._getCacheId()] = field
 
   def _getTemplateFieldCache(self):
-    if self.aq_parent:
+    parent = self.aq_parent
+    if parent is not None:
+      return getTransactionalVariable(self)[self._getCacheId()].__of__(parent)
+    else:
       raise KeyError
-    return getTransactionalVariable(self)[self._getCacheId()].__of__(self.aq_parent)
 
 
 #