diff --git a/disco/types/channel.py b/disco/types/channel.py
index 2c2ffb4..9f4a9a5 100644
--- a/disco/types/channel.py
+++ b/disco/types/channel.py
@@ -162,18 +162,27 @@ class Channel(SlottedModel, Permissible):
         member = self.guild.get_member(user)
         base = self.guild.get_permissions(member)
 
-        ow_everyone = self.overwrites.get(self.guild_id)
-        if ow_everyone:
-            base += ow_everyone.compiled
-
+        # First grab and apply the everyone overwrite
+        everyone = self.overwrites.get(self.guild_id)
+        if everyone:
+            base -= everyone.deny
+            base += everyone.allow
+
+        denies = 0
+        allows = 0
         for role_id in member.roles:
-            ow_role = self.overwrites.get(role_id)
-            if ow_role:
-                base += ow_role.compiled
+            overwrite = self.overwrites.get(role_id)
+            if overwrite:
+                denies |= overwrite.deny
+                allows |= overwrite.allow
+
+        base -= denies
+        base += allows
 
         ow_member = self.overwrites.get(member.user.id)
         if ow_member:
-            base += ow_member.compiled
+            base -= ow_member.deny
+            base += ow_member.allow
 
         return base
 
@@ -200,7 +209,7 @@ class Channel(SlottedModel, Permissible):
         """
         Whether this channel is an NSFW channel.
         """
-        return self.type == ChannelType.GUILD_TEXT and (self.nsfw or NSFW_RE.match(self.name))
+        return bool(self.type == ChannelType.GUILD_TEXT and (self.nsfw or NSFW_RE.match(self.name)))
 
     @property
     def is_voice(self):
diff --git a/disco/types/guild.py b/disco/types/guild.py
index d72e2f9..8df519c 100644
--- a/disco/types/guild.py
+++ b/disco/types/guild.py
@@ -357,6 +357,7 @@ class Guild(SlottedModel, Permissible):
         if self.owner_id == member.id:
             return PermissionValue(Permissions.ADMINISTRATOR)
 
+        # Our value starts with the guilds default (@everyone) role permissions
         value = PermissionValue(self.roles.get(self.id).permissions)
 
         # Iterate over all roles the user has (plus the @everyone role)
diff --git a/tests/types/channel.py b/tests/types/channel.py
index 88695ea..33cebcf 100644
--- a/tests/types/channel.py
+++ b/tests/types/channel.py
@@ -1,25 +1,23 @@
-from unittest import TestCase
-
 from disco.types.channel import Channel, ChannelType
 
 
-class TestChannel(TestCase):
-    def test_deprecated_nsfw_channel(self):
-        channel = Channel(
-            name='nsfw-testing',
-            type=ChannelType.GUILD_TEXT)
-        self.assertTrue(channel.is_nsfw)
+def test_deprecated_nsfw_channel():
+    channel = Channel(
+        name='nsfw-testing',
+        type=ChannelType.GUILD_TEXT)
+    assert channel.is_nsfw
+
+    channel = Channel(
+        name='nsfw-testing',
+        type=ChannelType.GUILD_VOICE)
+    assert not channel.is_nsfw
 
-        channel = Channel(
-            name='nsfw-testing',
-            type=ChannelType.GUILD_VOICE)
-        self.assertFalse(channel.is_nsfw)
+    channel = Channel(
+        name='nsfw_testing',
+        type=ChannelType.GUILD_TEXT)
+    assert not channel.is_nsfw
 
-        channel = Channel(
-            name='nsfw_testing',
-            type=ChannelType.GUILD_TEXT)
-        self.assertFalse(channel.is_nsfw)
 
-    def test_nsfw_channel(self):
-        channel = Channel(name='test', nsfw=True, type=ChannelType.GUILD_TEXT)
-        assert channel.is_nsfw
+def test_nsfw_channel():
+    channel = Channel(name='test', nsfw=True, type=ChannelType.GUILD_TEXT)
+    assert channel.is_nsfw