diff --git a/alexandria/core/models.py b/alexandria/core/models.py
index 5e70bba6..df6450ab 100644
--- a/alexandria/core/models.py
+++ b/alexandria/core/models.py
@@ -211,7 +211,7 @@ class Meta:
         ordering = ["-created_at"]
 
 
-@receiver(models.signals.pre_delete, sender=File)
+@receiver(models.signals.post_delete, sender=File)
 def auto_delete_file_on_delete(sender, instance, **kwargs):
     """Delete file from filesystem when `File` object is deleted."""
 
diff --git a/alexandria/core/utils.py b/alexandria/core/utils.py
index ec00b6fa..7e51f191 100644
--- a/alexandria/core/utils.py
+++ b/alexandria/core/utils.py
@@ -11,7 +11,7 @@
 from alexandria.core.models import File
 
 
-def create_thumbnail(_file):
+def create_thumbnail(_file: File):
     with NamedTemporaryFile() as tmp:
         temp_file = Path(tmp.name)
         manager = PreviewManager(str(temp_file.parent))
@@ -33,7 +33,7 @@ def create_thumbnail(_file):
 
     with path_to_preview_image.open("rb") as thumb:
         thumb_file = File.objects.create(
-            name=f"{_file.name}.jpg",
+            name=f"{_file.name}_preview.jpg",
             document=_file.document,
             variant=File.Variant.THUMBNAIL.value,
             original=_file,