diff --git a/CHANGES.txt b/CHANGES.txt
index 6271f285..46b201f9 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,6 +1,9 @@
 1.0b1 (unreleased)
 ==================
 
+- Fix password check for users created prior to switching to ``bcrypt``.
+  See https://github.com/Pylons/substanced/pull/316
+
 - Fix ``tznames_widget``, b0rken seemingly forever under Python3.
   See https://github.com/Pylons/substanced/pull/314
 
diff --git a/substanced/principal/__init__.py b/substanced/principal/__init__.py
index 9a00b657..c5116bf3 100644
--- a/substanced/principal/__init__.py
+++ b/substanced/principal/__init__.py
@@ -407,17 +407,23 @@ def timezone(self):
         return pytz.timezone(self.tzname)
 
     def check_password(self, password):
-        """ Checks if the plaintext password passed as ``password`` matches
-        this user's stored, encrypted password.  Returns ``True`` or
-        ``False``."""
+        """Check plaintext ``password`` against stored, hashed password.
+        """
         statsd_gauge('check_password', 1)
+
         if len(password) > 4096:
             # avoid DOS ala
             # https://www.djangoproject.com/weblog/2013/sep/15/security/
             raise ValueError('Not checking password > 4096 bytes')
+
         if isinstance(password, str):
             password = password.encode('utf-8')
-        return bcrypt.checkpw(password, self.password)
+
+        hashed = self.password
+        if isinstance(hashed, str):
+            hashed = hashed.encode('utf-8')
+
+        return bcrypt.checkpw(password, hashed)
 
     def set_password(self, password):
         self.password = self.hash_new_password(password)
diff --git a/substanced/principal/tests/test_principal.py b/substanced/principal/tests/test_principal.py
index 36090cfc..5d83a1c4 100644
--- a/substanced/principal/tests/test_principal.py
+++ b/substanced/principal/tests/test_principal.py
@@ -376,6 +376,14 @@ def test_check_password(self):
         self.assertTrue(inst.check_password('abc'))
         self.assertFalse(inst.check_password('abcdef'))
 
+    def test_check_password_w_str(self):
+        inst = self._makeOne('abc')
+        assert isinstance(inst.password, bytes)
+        # See https://github.com/Pylons/substanced/issues/315
+        inst.password = inst.password.decode('utf8')
+        self.assertTrue(inst.check_password('abc'))
+        self.assertFalse(inst.check_password('abcdef'))
+
     def test_check_password_gt_4096_bytes(self):
         inst = self._makeOne('abc')
         self.assertRaises(ValueError, inst.check_password, 'a'*4097)