diff --git a/onioningestor/onion.py b/onioningestor/onion.py
index 8e814ee..aa56a3e 100644
--- a/onioningestor/onion.py
+++ b/onioningestor/onion.py
@@ -1,3 +1,5 @@
+import re
+import operator
 from datetime import datetime as dt
 
 class Onion(object):
@@ -12,6 +14,16 @@ class Onion(object):
         self.datetime = dt.now()
         self.operators = {}
 
+    url = property(operator.attrgetter('_url'))
+
+    @url.setter
+    def url(self, domain):
+        onion_pattern = re.compile(r'([a-z2-7]{16,56}\.onion)')
+        if onion_pattern.match(domain):
+            self._url = domain
+        else:
+            raise Exception("Onion domain pattern does not match")
+
     def set_operator(self, response):
         self.operators.update(response)
 
diff --git a/onioningestor/operators/__init__.py b/onioningestor/operators/__init__.py
index 574ac55..6aa6201 100644
--- a/onioningestor/operators/__init__.py
+++ b/onioningestor/operators/__init__.py
@@ -113,7 +113,7 @@ class Operator:
                     type='domain',
                     status='offline',
                     monitor=False,
-                    denylist=False)))
+                    denylist="")))
 
     def process(self, onion):
         """Process all applicable onions."""
diff --git a/onioningestor/sources/simplefile.py b/onioningestor/sources/simplefile.py
index 6c420b4..8442066 100644
--- a/onioningestor/sources/simplefile.py
+++ b/onioningestor/sources/simplefile.py
@@ -38,7 +38,7 @@ class Plugin(Source):
                             type='domain',
                             status='offline',
                             monitor=False,
-                            denylist=False)
+                            denylist="")
                         )
                     )