diff --git a/app/accept_invite/rest.py b/app/accept_invite/rest.py
index 25855ecc8..f7c552d34 100644
--- a/app/accept_invite/rest.py
+++ b/app/accept_invite/rest.py
@@ -33,7 +33,9 @@ def get_invited_user_by_token(token):
                                       current_app.config['DANGEROUS_SALT'],
                                       max_age_seconds)
     except SignatureExpired:
-        errors = {'invitation': ['Invitation has expired']}
+        errors = {'invitation':
+                  ['Your invitation to GOV.UK Notify has expired. '
+                   'Please ask the person that invited you to send you another one']}
         raise InvalidRequest(errors, status_code=400)
 
     invited_user = get_invited_user_by_id(invited_user_id)
diff --git a/tests/app/accept_invite/test_accept_invite_rest.py b/tests/app/accept_invite/test_accept_invite_rest.py
index 2df8c185f..3fbc80079 100644
--- a/tests/app/accept_invite/test_accept_invite_rest.py
+++ b/tests/app/accept_invite/test_accept_invite_rest.py
@@ -1,6 +1,5 @@
 import uuid
 
-import pytest
 from flask import json
 from freezegun import freeze_time
 from notifications_utils.url_safe_token import generate_token
@@ -20,7 +19,9 @@ def test_accept_invite_for_expired_token_returns_400(notify_api, sample_invited_
         assert response.status_code == 400
         json_resp = json.loads(response.get_data(as_text=True))
         assert json_resp['result'] == 'error'
-        assert json_resp['message'] == {'invitation': ['Invitation has expired']}
+        assert json_resp['message'] == {'invitation': [
+            'Your invitation to GOV.UK Notify has expired. '
+            'Please ask the person that invited you to send you another one']}
 
 
 def test_accept_invite_returns_200_when_token_valid(notify_api, sample_invited_user):