diff --git a/gui/qt/main_window.py b/gui/qt/main_window.py
index d6e5ace06..b962e2175 100644
--- a/gui/qt/main_window.py
+++ b/gui/qt/main_window.py
@@ -879,7 +879,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
             self.show_error(_('No message or amount'))
             return False
         i = self.expires_combo.currentIndex()
-        expiration = map(lambda x: x[1], expiration_values)[i]
+        expiration = list(map(lambda x: x[1], expiration_values))[i]
         req = self.wallet.make_payment_request(addr, amount, message, expiration)
         self.wallet.add_payment_request(req, self.config)
         self.sign_payment_request(addr)