diff --git a/addons/website_forum/models/forum_forum.py b/addons/website_forum/models/forum_forum.py
index bed3662483d..ff5828a6e5d 100644
--- a/addons/website_forum/models/forum_forum.py
+++ b/addons/website_forum/models/forum_forum.py
@@ -233,18 +233,19 @@ class Forum(models.Model):
         post_tags = []
         existing_keep = []
         user = self.env.user
-        for tag in (tag for tag in tags.split(',') if tag):
-            if tag.startswith('_'):  # it's a new tag
+        for tag_id_or_new_name in (tag.strip() for tag in tags.split(',') if tag and tag.strip()):
+            if tag_id_or_new_name.startswith('_'):  # it's a new tag
+                tag_name = tag_id_or_new_name[1:]
                 # check that not already created meanwhile or maybe excluded by the limit on the search
-                tag_ids = Tag.search([('name', '=', tag[1:]), ('forum_id', '=', self.id)])
+                tag_ids = Tag.search([('name', '=', tag_name), ('forum_id', '=', self.id)], limit=1)
                 if tag_ids:
-                    existing_keep.append(int(tag_ids[0]))
+                    existing_keep.append(tag_ids.id)
                 else:
                     # check if user have Karma needed to create need tag
-                    if user.exists() and user.karma >= self.karma_tag_create and len(tag) and len(tag[1:].strip()):
-                        post_tags.append((0, 0, {'name': tag[1:], 'forum_id': self.id}))
+                    if user.exists() and user.karma >= self.karma_tag_create and tag_name:
+                        post_tags.append((0, 0, {'name': tag_name, 'forum_id': self.id}))
             else:
-                existing_keep.append(int(tag))
+                existing_keep.append(int(tag_id_or_new_name))
         post_tags.insert(0, [6, 0, existing_keep])
         return post_tags