diff --git a/forwardport/__manifest__.py b/forwardport/__manifest__.py
index c91fe427..f308a55e 100644
--- a/forwardport/__manifest__.py
+++ b/forwardport/__manifest__.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 {
     'name': 'forward port bot',
+    'version': '1.1',
     'summary': "A port which forward ports successful PRs.",
     'depends': ['runbot_merge'],
     'data': [
diff --git a/forwardport/migrations/13.0.1.1/post-reminder-date.py b/forwardport/migrations/13.0.1.1/post-reminder-date.py
new file mode 100644
index 00000000..36d131a8
--- /dev/null
+++ b/forwardport/migrations/13.0.1.1/post-reminder-date.py
@@ -0,0 +1,10 @@
+def migrate(cr, version):
+    """ Set the merge_date field to the current write_date, and reset
+    the backoff to its default so we reprocess old PRs properly.
+    """
+    cr.execute("""
+        UPDATE runbot_merge_pull_requests
+           SET merge_date = write_date,
+               reminder_backoff_factor = -4
+         WHERE state = 'merged'
+    """)
diff --git a/forwardport/migrations/13.0.1.1/pre-tagging.py b/forwardport/migrations/13.0.1.1/pre-tagging.py
new file mode 100644
index 00000000..ef2ad801
--- /dev/null
+++ b/forwardport/migrations/13.0.1.1/pre-tagging.py
@@ -0,0 +1,2 @@
+def migrate(cr, version):
+    cr.execute("delete from ir_model where model = 'forwardport.tagging'")
diff --git a/forwardport/models/forwardport.py b/forwardport/models/forwardport.py
index 3a0daab8..e58091b8 100644
--- a/forwardport/models/forwardport.py
+++ b/forwardport/models/forwardport.py
@@ -141,7 +141,7 @@ class DeleteBranches(models.Model, Queue):
     def _search_domain(self):
         cutoff = self.env.context.get('forwardport_merged_before') \
              or fields.Datetime.to_string(datetime.now() - MERGE_AGE)
-        return [('pr_id.write_date', '<', cutoff)]
+        return [('pr_id.merge_date', '<', cutoff)]
 
     def _process_item(self):
         _deleter.info(
diff --git a/forwardport/models/project.py b/forwardport/models/project.py
index 417787c8..a1454d3c 100644
--- a/forwardport/models/project.py
+++ b/forwardport/models/project.py
@@ -25,7 +25,7 @@ import re
 import subprocess
 import tempfile
 
-import dateutil
+import dateutil.relativedelta
 import requests
 
 from odoo import _, models, fields, api
@@ -188,6 +188,7 @@ class PullRequests(models.Model):
     )
     source_id = fields.Many2one('runbot_merge.pull_requests', index=True, help="the original source of this FP even if parents were detached along the way")
     reminder_backoff_factor = fields.Integer(default=-4)
+    merge_date = fields.Datetime()
 
     fw_policy = fields.Selection([
         ('ci', "Normal"),
@@ -218,6 +219,8 @@ class PullRequests(models.Model):
             )[-1].id
         if vals.get('parent_id') and 'source_id' not in vals:
             vals['source_id'] = self.browse(vals['parent_id'])._get_root().id
+        if vals.get('state') == 'merged':
+            vals['merge_date'] = fields.Datetime.now()
         return super().create(vals)
 
     def write(self, vals):
@@ -240,6 +243,8 @@ class PullRequests(models.Model):
 
         if vals.get('parent_id') and 'source_id' not in vals:
             vals['source_id'] = self.browse(vals['parent_id'])._get_root().id
+        if vals.get('state') == 'merged':
+            vals['merge_date'] = fields.Datetime.now()
         r = super().write(vals)
         if self.env.context.get('forwardport_detach_warn', True):
             for p in with_parents:
@@ -985,12 +990,12 @@ stderr:
             ('source_id', '!=', False),
             # active
             ('state', 'not in', ['merged', 'closed']),
-            # last updated more than <cutoff> ago
-            ('write_date', '<', cutoff),
+            # original merged more than <cutoff> ago
+            ('source_id.merge_date', '<', cutoff),
         ], order='source_id, id'), lambda p: p.source_id):
             backoff = dateutil.relativedelta.relativedelta(days=2**source.reminder_backoff_factor)
             prs = list(prs)
-            if all(p.write_date > (cutoff_dt - backoff) for p in prs):
+            if source.merge_date > (cutoff_dt - backoff):
                 continue
             source.reminder_backoff_factor += 1
             self.env['runbot_merge.pull_requests.feedback'].create({
diff --git a/forwardport/tests/test_simple.py b/forwardport/tests/test_simple.py
index a211d639..56d1e0b2 100644
--- a/forwardport/tests/test_simple.py
+++ b/forwardport/tests/test_simple.py
@@ -1,6 +1,5 @@
 # -*- coding: utf-8 -*-
 import collections
-import sys
 import time
 from datetime import datetime, timedelta
 from operator import itemgetter
@@ -9,7 +8,8 @@ import pytest
 
 from utils import *
 
-FAKE_PREV_WEEK = (datetime.now() + timedelta(days=1)).strftime('%Y-%m-%d %H:%M:%S')
+FMT = '%Y-%m-%d %H:%M:%S'
+FAKE_PREV_WEEK = (datetime.now() + timedelta(days=1)).strftime(FMT)
 
 # need:
 # * an odoo server
@@ -56,6 +56,12 @@ def test_straightforward_flow(env, config, make_repo, users):
         # use rebase-ff (instead of rebase-merge) so we don't have to dig in
         # parents of the merge commit to find the cherrypicks
         pr.post_comment('hansen r+ rebase-ff', config['role_reviewer']['token'])
+    pr_id = env['runbot_merge.pull_requests'].search([
+        ('repository.name', '=', prod.name),
+        ('number', '=', pr.number),
+    ])
+    assert not pr_id.merge_date,\
+        "PR obviously shouldn't have a merge date before being merged"
 
     env.run_crons()
     with prod:
@@ -65,6 +71,10 @@ def test_straightforward_flow(env, config, make_repo, users):
     # should merge the staging then create the FP PR
     env.run_crons()
 
+    assert datetime.now() - datetime.strptime(pr_id.merge_date, FMT) <= timedelta(minutes=1),\
+        "check if merge date was set about now (within a minute as crons and " \
+        "RPC calls yield various delays before we're back)"
+
     p_1_merged = prod.commit('a')
 
     assert p_1_merged.id != p_1