diff --git a/ufl/functionspace.py b/ufl/functionspace.py
index ef57e740b..dc449645f 100644
--- a/ufl/functionspace.py
+++ b/ufl/functionspace.py
@@ -36,7 +36,7 @@ def ufl_sub_spaces(self):
 class BaseFunctionSpace(AbstractFunctionSpace, UFLObject):
     """Base function space."""
 
-    def __init__(self, domain, element, label=None):
+    def __init__(self, domain, element, label=""):
         """Initialise."""
         if domain is None:
             # DOLFIN hack
@@ -50,14 +50,15 @@ def __init__(self, domain, element, label=None):
             else:
                 if element.cell != domain_cell:
                     raise ValueError("Non-matching cell of finite element and domain.")
-
+        
         AbstractFunctionSpace.__init__(self)
+        self._label = label
         self._ufl_domain = domain
         self._ufl_element = element
 
     def label(self):
         """Return label of boundary domains to differentiate restricted and unrestricted"""
-        return self.label
+        return self._label
 
     def ufl_sub_spaces(self):
         """Return ufl sub spaces."""
@@ -149,7 +150,7 @@ class DualSpace(BaseFunctionSpace, UFLObject):
     _primal = False
     _dual = True
 
-    def __init__(self, domain, element, label=None):
+    def __init__(self, domain, element, label=""):
         """Initialise."""
         BaseFunctionSpace.__init__(self, domain, element, label)