diff --git a/app/notify_client/user_api_client.py b/app/notify_client/user_api_client.py
index 0b1970d06..8784673f6 100644
--- a/app/notify_client/user_api_client.py
+++ b/app/notify_client/user_api_client.py
@@ -149,7 +149,7 @@ class UserApiClient(NotifyAdminAPIClient):
     def activate_user(self, user):
         if user.state == 'pending':
             url = "/user/{}/activate".format(user.id)
-            user_data = self.post(url)
+            user_data = self.post(url, data=None)
             return User(user_data['data'], max_failed_login_count=self.max_failed_login_count)
         else:
             return user
diff --git a/tests/app/notify_client/test_user_client.py b/tests/app/notify_client/test_user_client.py
index 5f2f728ec..857f44faa 100644
--- a/tests/app/notify_client/test_user_client.py
+++ b/tests/app/notify_client/test_user_client.py
@@ -42,7 +42,7 @@ def test_client_activates_if_pending(mocker, api_user_pending):
 
     client.activate_user(api_user_pending)
 
-    mock_post.assert_called_once_with('/user/{}/activate'.format(api_user_pending.id))
+    mock_post.assert_called_once_with('/user/{}/activate'.format(api_user_pending.id), data=None)
 
 
 def test_client_doesnt_activate_if_already_active(mocker, api_user_active):