diff --git a/boards/views.py b/boards/views.py
--- a/boards/views.py
+++ b/boards/views.py
@@ -119,6 +119,8 @@ def tag(request, tag_name, page=0):
     if request.method == 'POST':
         form = ThreadForm(request.POST, request.FILES,
                           error_class=PlainErrorList)
+        form.session = request.session
+
         if form.is_valid():
             return _new_post(request, form)
         if form.need_to_ban:
diff --git a/todo.txt b/todo.txt
--- a/todo.txt
+++ b/todo.txt
@@ -10,4 +10,4 @@
 [NOT STARTED] Thread autoupdate (JS + API)
 
 = Bugs =
-[NOT STARTED] Fix bug with creating threads from tag view
+[DONE] Fix bug with creating threads from tag view