diff --git a/swh/lister/nixguix/lister.py b/swh/lister/nixguix/lister.py
--- a/swh/lister/nixguix/lister.py
+++ b/swh/lister/nixguix/lister.py
@@ -242,12 +242,30 @@
                     url,
                 )
 
+        origin = urls[0]
+
         content_type = response.headers.get("Content-Type")
         if content_type:
             logger.debug("Content-Type: %s", content_type)
             if content_type == "application/json":
-                return False, urls[0]
-            return content_type.startswith(POSSIBLE_TARBALL_MIMETYPES), urls[0]
+                return False, origin
+            return content_type.startswith(POSSIBLE_TARBALL_MIMETYPES), origin
+
+        content_disposition = response.headers.get("Content-Disposition")
+        if content_disposition:
+            logger.debug("Content-Disposition: %s", content_disposition)
+            content_disposition_type, filename_type = content_disposition.split("; ")
+            assert content_disposition_type == "attachment"
+            _, filename = filename_type.split("=")
+
+            return (
+                url_endswith(
+                    urlparse(filename),
+                    TARBALL_EXTENSIONS,
+                    raise_when_no_extension=False,
+                ),
+                origin,
+            )
 
         raise ArtifactNatureUndetected(
             f"Cannot determine artifact type from url <{url}>"
diff --git a/swh/lister/nixguix/tests/data/sources-success.json b/swh/lister/nixguix/tests/data/sources-success.json
--- a/swh/lister/nixguix/tests/data/sources-success.json
+++ b/swh/lister/nixguix/tests/data/sources-success.json
@@ -272,6 +272,13 @@
         "https://codeload.github.com/fifengine/fifechan/tar.gz/0.1.5"
       ],
       "integrity": "sha256-Kb5f9LN54vxPiO99i8FyNCEw3T53owYfZMinXv5OunM="
+    },
+    {
+      "type": "url",
+      "urls": [
+        "https://codeload.github.com/unknown-horizons/unknown-horizons/tar.gz/2019.1"
+      ],
+      "integrity": "sha256-pBf9PTQiEv0ZDk8hvoLvE8EOHtfCiPu+RuRiAM895Ng="
     }
   ],
   "version": "1",
diff --git a/swh/lister/nixguix/tests/test_lister.py b/swh/lister/nixguix/tests/test_lister.py
--- a/swh/lister/nixguix/tests/test_lister.py
+++ b/swh/lister/nixguix/tests/test_lister.py
@@ -238,6 +238,12 @@
             "Content-Type": "application/x-gzip",
         },
     )
+    requests_mock.head(
+        "https://codeload.github.com/unknown-horizons/unknown-horizons/tar.gz/2019.1",
+        headers={
+            "Content-Disposition": "attachment; filename=unknown-horizons-2019.1.tar.gz",
+        },
+    )
 
     expected_visit_types = defaultdict(int)
     # origin upstream is added as origin