diff --git a/archivebox/core/migrations/0008_auto_20210104_1458.py b/archivebox/core/migrations/0008_auto_20210105_1421.py
similarity index 68%
rename from archivebox/core/migrations/0008_auto_20210104_1458.py
rename to archivebox/core/migrations/0008_auto_20210105_1421.py
index 83914b3b..e5b3387d 100644
--- a/archivebox/core/migrations/0008_auto_20210104_1458.py
+++ b/archivebox/core/migrations/0008_auto_20210105_1421.py
@@ -1,4 +1,4 @@
-# Generated by Django 3.1.3 on 2021-01-04 14:58
+# Generated by Django 3.1.3 on 2021-01-05 14:21
 
 from django.db import migrations, models
 
@@ -13,6 +13,6 @@ class Migration(migrations.Migration):
         migrations.AlterField(
             model_name='archiveresult',
             name='cmd_version',
-            field=models.CharField(default='', max_length=32),
+            field=models.CharField(blank=True, default=None, max_length=32, null=True),
         ),
     ]
diff --git a/archivebox/core/models.py b/archivebox/core/models.py
index 9238f7f8..13d75b66 100644
--- a/archivebox/core/models.py
+++ b/archivebox/core/models.py
@@ -181,7 +181,7 @@ class ArchiveResult(models.Model):
     snapshot = models.ForeignKey(Snapshot, on_delete=models.CASCADE)
     cmd = JSONField()
     pwd = models.CharField(max_length=256)
-    cmd_version = models.CharField(max_length=32, default="")
+    cmd_version = models.CharField(max_length=32, default=None, null=True, blank=True)
     output = models.CharField(max_length=512)
     start_ts = models.DateTimeField()
     end_ts = models.DateTimeField()