diff --git a/apps/resm/models.py b/apps/resm/models.py
index e2e48a0..fb7685e 100644
--- a/apps/resm/models.py
+++ b/apps/resm/models.py
@@ -44,13 +44,16 @@ class Paper(BaseModel):
 
     def init_save_dir(self):
         publication_date = self.publication_date
-        paper_dir = os.path.join(
-            settings.BASE_DIR,
-            "media/papers",
-            str(publication_date.year),
-            str(publication_date.month),
-            str(publication_date.day)
-        )
+        if publication_date is None:
+            paper_dir = os.path.join(settings.BASE_DIR, "media/papers", "unknown")
+        else:
+            paper_dir = os.path.join(
+                settings.BASE_DIR,
+                "media/papers",
+                str(publication_date.year),
+                str(publication_date.month),
+                str(publication_date.day)
+            )
         os.makedirs(paper_dir, exist_ok=True)
         return paper_dir
     
diff --git a/apps/resm/tasks.py b/apps/resm/tasks.py
index 4a857f1..a02271f 100644
--- a/apps/resm/tasks.py
+++ b/apps/resm/tasks.py
@@ -11,7 +11,6 @@ from lxml import etree
 from celery import current_app
 from datetime import datetime
 import random
-import time
 
 # config.email = "caoqianming@foxmail.com"
 config.email = "caoqianming@ctc.ac.cn"
@@ -320,6 +319,7 @@ def download_pdf(paper_id):
         paper.fetch_status = 'downloading'
         paper.save(update_fields=['fetch_status', 'update_time'])
         msg = "没有下载渠道"
+        current_from = ""
         if paper.oa_url:
             current_from = "oa_url"
             msg = save_pdf_from_oa_url(paper)
@@ -328,7 +328,7 @@ def download_pdf(paper_id):
         #     msg = save_pdf_from_openalex(paper)
         return msg, current_from
     finally:
-        if paper.fetch_status == "downloading":
+        if paper and paper.fetch_status == "downloading":
             paper.fetch_status = original_status
             paper.save(update_fields=['fetch_status', 'update_time'])