diff --git a/payment_sixpay/README.md b/payment_sixpay/README.md
index 9cfb1dc..9420dff 100644
--- a/payment_sixpay/README.md
+++ b/payment_sixpay/README.md
@@ -8,6 +8,10 @@ they are automatically sent back to Indico.
 
 ## Changelog
 
+### 3.1.1
+
+- Ignore pending transactions once they expired
+
 ### 3.1
 
 - Adapt to Indico 3.1 changes
diff --git a/payment_sixpay/indico_payment_sixpay/plugin.py b/payment_sixpay/indico_payment_sixpay/plugin.py
index 3f37203..5fe8883 100644
--- a/payment_sixpay/indico_payment_sixpay/plugin.py
+++ b/payment_sixpay/indico_payment_sixpay/plugin.py
@@ -5,8 +5,11 @@
 # them and/or modify them under the terms of the MIT License;
 # see the LICENSE file for more details.
 
+import dateutil.parser
+
 from indico.core.plugins import IndicoPlugin
 from indico.modules.events.payment import PaymentPluginMixin
+from indico.util.date_time import now_utc
 
 from indico_payment_sixpay.forms import EventSettingsForm, PluginSettingsForm
 
@@ -47,3 +50,8 @@ class SixpayPaymentPlugin(PaymentPluginMixin, IndicoPlugin):
         """Blueprint for URL endpoints with callbacks."""
         from indico_payment_sixpay.blueprint import blueprint
         return blueprint
+
+    def is_pending_transaction_expired(self, transaction):
+        if not (expiration := transaction.data.get('Init_PP_response', {}).get('Expiration')):
+            return False
+        return dateutil.parser.parse(expiration) <= now_utc()
diff --git a/payment_sixpay/setup.cfg b/payment_sixpay/setup.cfg
index a2ed86a..3ee2ca8 100644
--- a/payment_sixpay/setup.cfg
+++ b/payment_sixpay/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = indico-plugin-payment-sixpay
-version = 3.1
+version = 3.1.1
 description = SIXPay/Saferpay payments for Indico event registration fees
 long_description = file: README.md
 long_description_content_type = text/markdown; charset=UTF-8; variant=GFM