diff --git a/addons/website_forum/models/forum_post.py b/addons/website_forum/models/forum_post.py
index d9bf15487b0..5e514c89a5a 100644
--- a/addons/website_forum/models/forum_post.py
+++ b/addons/website_forum/models/forum_post.py
@@ -612,22 +612,19 @@ class Post(models.Model):
         return False
 
     def vote(self, upvote=True):
+        self.ensure_one()
         Vote = self.env['forum.post.vote']
-        vote_ids = Vote.search([('post_id', 'in', self._ids), ('user_id', '=', self._uid)])
-        new_vote = '1' if upvote else '-1'
-        voted_forum_ids = set()
-        if vote_ids:
-            for vote in vote_ids:
-                if upvote:
-                    new_vote = '0' if vote.vote == '-1' else '1'
-                else:
-                    new_vote = '0' if vote.vote == '1' else '-1'
-                vote.vote = new_vote
-                voted_forum_ids.add(vote.post_id.id)
-        for post_id in set(self._ids) - voted_forum_ids:
-            for post_id in self._ids:
-                Vote.create({'post_id': post_id, 'vote': new_vote})
-        return {'vote_count': self.vote_count, 'user_vote': new_vote}
+        existing_vote = Vote.search([('post_id', '=', self.id), ('user_id', '=', self._uid)])
+        new_vote_value = '1' if upvote else '-1'
+        if existing_vote:
+            if upvote:
+                new_vote_value = '0' if existing_vote.vote == '-1' else '1'
+            else:
+                new_vote_value = '0' if existing_vote.vote == '1' else '-1'
+            existing_vote.vote = new_vote_value
+        else:
+            Vote.create({'post_id': self.id, 'vote': new_vote_value})
+        return {'vote_count': self.vote_count, 'user_vote': new_vote_value}
 
     def convert_answer_to_comment(self):
         """ Tools to convert an answer (forum.post) to a comment (mail.message).
diff --git a/addons/website_forum/tests/test_forum_karma_access.py b/addons/website_forum/tests/test_forum_karma_access.py
index ea1f8a48f66..973862951f6 100644
--- a/addons/website_forum/tests/test_forum_karma_access.py
+++ b/addons/website_forum/tests/test_forum_karma_access.py
@@ -373,10 +373,50 @@ class TestForumKarma(TestForumCommon):
         self.assertEqual(post.state, 'active', 'website_forum: wrong state when validate a post after offensive')
 
     def test_vote(self):
+        def check_vote_records_count_and_integrity(expected_total_votes_count):
+            groups = self.env['forum.post.vote'].read_group([], fields=['__count'], groupby=['post_id', 'user_id'], lazy=False)
+            self.assertEqual(len(groups), expected_total_votes_count)
+            for post_user_group in groups:
+                self.assertEqual(post_user_group['__count'], 1)
+
+        check_vote_records_count_and_integrity(2)
         self.post.create_uid.karma = KARMA['ask']
-        self.user_portal.karma = KARMA['upv']
-        self.post.with_user(self.user_portal).vote(upvote=True)
-        self.assertEqual(self.post.create_uid.karma, KARMA['ask'] + KARMA['gen_que_upv'], 'website_forum: wrong karma generation of upvoted question author')
+        self.user_portal.karma = KARMA['dwv']
+        initial_vote_count = self.post.vote_count
+        post_as_portal = self.post.with_user(self.user_portal)
+        res = post_as_portal.vote(upvote=True)
+
+        self.assertEqual(res['user_vote'], '1')
+        self.assertEqual(res['vote_count'], initial_vote_count + 1)
+        self.assertEqual(post_as_portal.user_vote, 1)
+        self.assertEqual(
+            self.post.create_uid.karma,
+            KARMA['ask'] + KARMA['gen_que_upv'],
+            'website_forum: wrong karma generation of upvoted question author',
+        )
+
+        # On voting again with the same value, nothing changes
+        res = post_as_portal.vote(upvote=True)
+        self.assertEqual(res['vote_count'], initial_vote_count + 1)
+        self.assertEqual(res['user_vote'], '1')
+        self.post.invalidate_recordset()
+        self.assertEqual(post_as_portal.user_vote, 1)
+
+        # On reverting vote, vote cancels
+        res = post_as_portal.vote(upvote=False)
+        self.assertEqual(res['vote_count'], initial_vote_count)
+        self.assertEqual(res['user_vote'], '0')
+        self.post.invalidate_recordset()
+        self.assertEqual(post_as_portal.user_vote, 0)
+
+        # Everything works from "0" too
+        res = post_as_portal.vote(upvote=False)
+        self.assertEqual(res['vote_count'], initial_vote_count - 1)
+        self.assertEqual(res['user_vote'], '-1')
+        self.post.invalidate_recordset()
+        self.assertEqual(post_as_portal.user_vote, -1)
+
+        check_vote_records_count_and_integrity(3)
 
     @mute_logger('odoo.addons.base.models.ir_model', 'odoo.models')
     def test_vote_crash(self):