diff --git a/payment_paypal/indico_payment_paypal/controllers.py b/payment_paypal/indico_payment_paypal/controllers.py
index 82cfdbc..df6c21a 100644
--- a/payment_paypal/indico_payment_paypal/controllers.py
+++ b/payment_paypal/indico_payment_paypal/controllers.py
@@ -73,10 +73,10 @@ class RHPaypalIPN(RH):
                              data=request.form)
 
     def _verify_business(self):
-        expected = current_plugin.event_settings.get(self.registration.registration_form.event, 'business')
-        candidates = {request.form.get('business'),
-                      request.form.get('receiver_id'),
-                      request.form.get('receiver_email')}
+        expected = current_plugin.event_settings.get(self.registration.registration_form.event, 'business').lower()
+        candidates = {request.form.get('business', '').lower(),
+                      request.form.get('receiver_id', '').lower(),
+                      request.form.get('receiver_email', '').lower()}
         if expected in candidates:
             return True
         current_plugin.logger.warning("Unexpected business: %s not in %r (request data: %r)", expected, candidates,
diff --git a/payment_paypal/tests/controllers_test.py b/payment_paypal/tests/controllers_test.py
index d011825..5990717 100644
--- a/payment_paypal/tests/controllers_test.py
+++ b/payment_paypal/tests/controllers_test.py
@@ -28,7 +28,7 @@ def test_ipn_verify_business(formdata, expected, dummy_event):
     rh = RHPaypalIPN()
     rh.registration = MagicMock()
     rh.registration.registration_form.event = dummy_event
-    PaypalPaymentPlugin.event_settings.set(dummy_event, 'business', 'test')
+    PaypalPaymentPlugin.event_settings.set(dummy_event, 'business', 'TeST')
     request.form = formdata
     with PaypalPaymentPlugin.instance.plugin_context():
         assert rh._verify_business() == expected
@@ -88,6 +88,7 @@ def test_ipn_process(mocker, fail):
     mocker.patch('indico_payment_paypal.controllers.notify_amount_inconsistency')
     post.return_value.text = 'INVALID' if fail == 'verify' else 'VERIFIED'
     rh = RHPaypalIPN()
+    rh._verify_business = MagicMock()
     rh._is_transaction_duplicated = lambda: fail == 'dup_txn'
     rh.event = MagicMock(id=1)
     rh.registration = MagicMock()