diff --git a/gns3server/controller/appliance_manager.py b/gns3server/controller/appliance_manager.py
index 1b1209b69..f4ecdded5 100644
--- a/gns3server/controller/appliance_manager.py
+++ b/gns3server/controller/appliance_manager.py
@@ -254,6 +254,8 @@ class ApplianceManager:
                                         )
                                     try:
                                         image_in_db = await images_repo.save_verified_image(image_info)
+                                        if image_in_db is None:
+                                            raise ControllerError(f"Could not register image '{image_path}'")
                                         version_images[appliance_key] = self._image_reference(image_in_db)
                                     except SQLAlchemyError as e:
                                         raise ControllerError(f"Could not register image '{image_path}': {e}") from e
diff --git a/gns3server/utils/images.py b/gns3server/utils/images.py
index e6855a2b8..a7be91ae8 100644
--- a/gns3server/utils/images.py
+++ b/gns3server/utils/images.py
@@ -424,8 +424,8 @@ async def write_image(
                         f"File '{image_path}' already exists, "
                         f"please choose a different name or remove the existing image"
                     )
-                checksum = checksum.hexdigest()
-                duplicate_image = await images_repo.get_image_by_checksum(checksum, os.path.dirname(image_path))
+                checksum_str = checksum.hexdigest()
+                duplicate_image = await images_repo.get_image_by_checksum(checksum_str, os.path.dirname(image_path))
                 if duplicate_image:
                     raise InvalidImageError(
                         f"Image '{duplicate_image.filename}' with the same checksum "
@@ -439,7 +439,7 @@ async def write_image(
                         image_type=image_type,
                         image_size=image_size,
                         path=image_path,
-                        checksum=checksum,
+                        checksum=checksum_str,
                         checksum_algorithm="md5",
                         file_fingerprint=file_fingerprint,
                     )