diff --git a/apiserver/apiserver/api/serializers.py b/apiserver/apiserver/api/serializers.py
index d9fc0ff..2dbbf85 100644
--- a/apiserver/apiserver/api/serializers.py
+++ b/apiserver/apiserver/api/serializers.py
@@ -54,6 +54,8 @@ class TransactionSerializer(serializers.ModelSerializer):
             'last_seen_at',
             'user',
             'recorder',
+            'paypal_txn_id',
+            'paypal_payer_id',
         ]
 
     def create(self, validated_data):
diff --git a/apiserver/apiserver/api/views.py b/apiserver/apiserver/api/views.py
index fabcdfd..376528b 100644
--- a/apiserver/apiserver/api/views.py
+++ b/apiserver/apiserver/api/views.py
@@ -209,13 +209,21 @@ class TransactionViewSet(Base, List, Create, Retrieve, Update):
         member = get_object_or_404(models.Member, id=member_id)
         utils.tally_membership_months(member)
 
+    def train_paypal_hint(self, tx):
+        if tx.paypal_payer_id and tx.member_id:
+            models.PayPalHint.objects.update_or_create(
+                account=tx.paypal_payer_id,
+                defaults=dict(member_id=tx.member_id),
+            )
+
     def perform_create(self, serializer):
         serializer.save(recorder=self.request.user)
         self.retally_membership()
 
     def perform_update(self, serializer):
-        serializer.save()
+        tx = serializer.save()
         self.retally_membership()
+        self.train_paypal_hint(tx)
 
     def list(self, request):
         if not is_admin_director(self.request.user):