diff --git a/changelog.d/8417.feature b/changelog.d/8417.feature
new file mode 100644
index 000000000..17549c3df
--- /dev/null
+++ b/changelog.d/8417.feature
@@ -0,0 +1 @@
+Add a config option to specify a whitelist of domains that a user can be redirected to after validating their email or phone number.
\ No newline at end of file
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index c3ce0f625..9245214f3 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -103,8 +103,9 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
-        # Raise if the provided next_link value isn't valid
-        assert_valid_next_link(self.hs, next_link)
+        if next_link:
+            # Raise if the provided next_link value isn't valid
+            assert_valid_next_link(self.hs, next_link)
 
         # The email will be sent to the stored address.
         # This avoids a potential account hijack by requesting a password reset to
@@ -379,8 +380,9 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
-        # Raise if the provided next_link value isn't valid
-        assert_valid_next_link(self.hs, next_link)
+        if next_link:
+            # Raise if the provided next_link value isn't valid
+            assert_valid_next_link(self.hs, next_link)
 
         existing_user_id = await self.store.get_user_id_by_threepid("email", email)
 
@@ -453,8 +455,9 @@ class MsisdnThreepidRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
-        # Raise if the provided next_link value isn't valid
-        assert_valid_next_link(self.hs, next_link)
+        if next_link:
+            # Raise if the provided next_link value isn't valid
+            assert_valid_next_link(self.hs, next_link)
 
         existing_user_id = await self.store.get_user_id_by_threepid("msisdn", msisdn)
 
diff --git a/tests/rest/client/v2_alpha/test_account.py b/tests/rest/client/v2_alpha/test_account.py
index 93f899d86..ae2cd67f3 100644
--- a/tests/rest/client/v2_alpha/test_account.py
+++ b/tests/rest/client/v2_alpha/test_account.py
@@ -732,6 +732,12 @@ class ThreepidEmailRestTestCase(unittest.HomeserverTestCase):
     @override_config({"next_link_domain_whitelist": ["example.com", "example.org"]})
     def test_next_link_domain_whitelist(self):
         """Tests next_link parameters must fit the whitelist if provided"""
+
+        # Ensure not providing a next_link parameter still works
+        self._request_token(
+            "something@example.com", "some_secret", next_link=None, expect_code=200,
+        )
+
         self._request_token(
             "something@example.com",
             "some_secret",