diff --git a/wsme/controller.py b/wsme/controller.py
index 303dd6e..e445822 100644
--- a/wsme/controller.py
+++ b/wsme/controller.py
@@ -260,14 +260,15 @@ class WSRoot(object):
 
     def _format_exception(self, excinfo):
         """Extract informations that can be sent to the client."""
-        if isinstance(excinfo[1], exc.ClientSideError):
+        error = excinfo[1]
+        if isinstance(error, exc.ClientSideError):
             r = dict(faultcode="Client",
-                     faultstring=unicode(excinfo[1]))
+                     faultstring=error.faultstring)
             log.warning("Client-side error: %s" % r['faultstring'])
             r['debuginfo'] = None
             return r
         else:
-            faultstring = str(excinfo[1])
+            faultstring = str(error)
             debuginfo = "\n".join(traceback.format_exception(*excinfo))
 
             log.error('Server-side error: "%s". Detail: \n%s' % (
diff --git a/wsme/exc.py b/wsme/exc.py
index 033d30b..d3eb496 100644
--- a/wsme/exc.py
+++ b/wsme/exc.py
@@ -5,11 +5,9 @@ if '_' not in __builtin__.__dict__:
 
 
 class ClientSideError(RuntimeError):
-    def __unicode__(self):
-        return RuntimeError.__str__(self)
-
-    def __str__(self):
-        return unicode(self).encode('utf8', 'ignore')
+    @property
+    def faultstring(self):
+        return str(self)
 
 
 class InvalidInput(ClientSideError):
@@ -18,7 +16,8 @@ class InvalidInput(ClientSideError):
         self.value = value
         self.msg = msg
 
-    def __unicode__(self):
+    @property
+    def faultstring(self):
         return _(u"Invalid input for field/attribute %s. Value: '%s'. %s") % (
                  self.fieldname, self.value, self.msg)
 
@@ -28,7 +27,8 @@ class MissingArgument(ClientSideError):
         self.argname = argname
         self.msg = msg
 
-    def __unicode__(self):
+    @property
+    def faultstring(self):
         return _(u'Missing argument: "%s"%s') % (
             self.argname, self.msg and ": " + self.msg or "")
 
@@ -38,7 +38,8 @@ class UnknownArgument(ClientSideError):
         self.argname = argname
         self.msg = msg
 
-    def __unicode__(self):
+    @property
+    def faultstring(self):
         return _(u'Unknown argument: "%s"%s') % (
             self.argname, self.msg and ": " + self.msg or "")
 
@@ -47,5 +48,6 @@ class UnknownFunction(ClientSideError):
     def __init__(self, name):
         self.name = name
 
-    def __unicode__(self):
+    @property
+    def faultstring(self):
         return _(u"Unknown function name: %s") % (self.name)
diff --git a/wsme/tests/test_exc.py b/wsme/tests/test_exc.py
new file mode 100644
index 0000000..42676f9
--- /dev/null
+++ b/wsme/tests/test_exc.py
@@ -0,0 +1,32 @@
+# encoding=utf8
+
+from wsme.exc import *
+
+
+def test_clientside_error():
+    e = ClientSideError("Test")
+
+    assert e.faultstring == "Test"
+
+
+def test_invalidinput():
+    e = InvalidInput('field', 'badvalue', "error message")
+
+    assert e.faultstring == \
+        u"Invalid input for field/attribute field. Value: 'badvalue'. " \
+        "error message", e.faultstring
+
+
+def test_missingargument():
+    e = MissingArgument('argname', "error message")
+
+    assert e.faultstring == \
+        u'Missing argument: "argname": error message', e.faultstring
+
+
+def test_unknownargument():
+    e = UnknownArgument('argname', "error message")
+
+    assert e.faultstring == \
+        u'Unknown argument: "argname": error message', e.faultstring
+