diff --git a/tests/test_unique_validator.py b/tests/test_unique_validator.py
index e03a511..7716b06 100644
--- a/tests/test_unique_validator.py
+++ b/tests/test_unique_validator.py
@@ -2,11 +2,17 @@
 from pytest import mark, raises
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import relationship
+from sqlalchemy_utils import PhoneNumberType
 from wtforms import Form
 from wtforms.fields import TextField
 
 from tests import MultiDict
-from wtforms_alchemy import ModelForm, QuerySelectField, Unique
+from wtforms_alchemy import (
+    ModelForm,
+    PhoneNumberField,
+    QuerySelectField,
+    Unique
+)
 
 base = declarative_base()
 
@@ -22,6 +28,10 @@ class User(base):
     id = sa.Column(sa.Integer, primary_key=True)
     name = sa.Column(sa.Unicode(255), unique=True)
     email = sa.Column(sa.Unicode(255))
+    phone = sa.Column(
+        PhoneNumberType(region='ES', max_length=25),
+        unique=True
+    )
     favorite_color_id = sa.Column(sa.Integer, sa.ForeignKey(Color.id))
     favorite_color = relationship(Color)
 
@@ -372,3 +382,16 @@ class MyForm(ModelForm):
 
         form = MyForm(MultiDict({'name': u'someone'}))
         assert form.validate()
+
+    def test_invalid_unique_phone_no_500_error(self):
+        class MyForm(ModelForm):
+            phone = PhoneNumberField(
+                validators=[Unique(User.phone)],
+                region='ES'
+            )
+
+        form = MyForm(MultiDict({'phone': u'abc$%·'}))
+        form.validate()
+        assert len(form.errors['phone']) == 2
+        assert 'Not a valid phone number value' in form.errors['phone']
+        assert 'Unable to check uniqueness.' in form.errors['phone']
diff --git a/wtforms_alchemy/validators.py b/wtforms_alchemy/validators.py
index cfee413..5addb4c 100644
--- a/wtforms_alchemy/validators.py
+++ b/wtforms_alchemy/validators.py
@@ -3,6 +3,7 @@
 import six
 from sqlalchemy import Column
 from sqlalchemy.orm.attributes import InstrumentedAttribute
+from sqlalchemy_utils import PhoneNumberParseException, PhoneNumberType
 from wtforms import ValidationError
 
 
@@ -25,13 +26,18 @@ class Unique(object):
         parameter.
     :param message:
         The error message.
+    :param message_uncheck
+        The error message when the attempt to check uniqueness cannot be
+        carried out, i.e. the query throws an exception.
     """
     field_flags = ('unique', )
 
-    def __init__(self, column, get_session=None, message=None):
+    def __init__(self, column, get_session=None, message=None,
+                 message_uncheck=u'Unable to check uniqueness.'):
         self.column = column
         self.message = message
         self.get_session = get_session
+        self.message_uncheck = message_uncheck
 
     @property
     def query(self):
@@ -76,7 +82,10 @@ def __call__(self, form, field):
         for field_name, column in columns:
             query = query.filter(column == form[field_name].data)
 
-        obj = query.first()
+        try:
+            obj = query.first()
+        except PhoneNumberParseException:
+            raise ValidationError(self.message_uncheck)
 
         if not hasattr(form, '_obj'):
             raise Exception(