diff --git a/swh/loader/package/functional/loader.py b/swh/loader/package/functional/loader.py
--- a/swh/loader/package/functional/loader.py
+++ b/swh/loader/package/functional/loader.py
@@ -6,7 +6,9 @@
 import json
 import requests
 
-from typing import Dict, Optional, Any
+from typing import Dict, Optional, Any, Mapping
+
+from swh.model import hashutil
 
 from swh.model.model import (
     Sha1Git, Revision, RevisionType
@@ -26,10 +28,16 @@
 
     def __init__(self, url, origin=None):
         super().__init__(url=url, origin=origin)
-        self.sources = self._retrieve_sources()['sources']
+        s = self._retrieve_sources()
+        self.sources = s['sources']
         self.provider_url = url
+        self.revision = s['revision']
 
     def _retrieve_sources(self) -> Dict[str, Any]:
+        """Download the sources.json file from self.url, parse it and return
+        the Dict.
+
+        """
         response = requests.get(self.url,
                                 allow_redirects=True)
         if response.status_code != 200:
@@ -62,6 +70,17 @@
                 return rev_id
         return None
 
+    def hook_branches(
+            self, branches: Dict[bytes, Mapping[str, Any]]) \
+            -> Dict[bytes, Mapping[str, Any]]:
+        branches.update({
+            b'evaluation': {
+                'target_type': 'revision',
+                'target': hashutil.hash_to_bytes(self.revision)
+            }
+        })
+        return branches
+
     def build_revision(self, a_metadata: Dict, uncompressed_path: str,
                        directory: Sha1Git) -> Optional[Revision]:
         return Revision(
diff --git a/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json b/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json
--- a/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json
+++ b/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json
@@ -9,5 +9,6 @@
       "url": [ "https://example.com/file.txt" ]
     }
  ],
-  "version": 1
+    "version": 1,
+    "revision": "cc4e04c26672dd74e5fd0fecb78b435fb55368f7"
 }
diff --git a/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json_visit1 b/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json_visit1
--- a/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json_visit1
+++ b/swh/loader/package/functional/tests/data/https_nix-community.github.io/nixpkgs-swh_sources.json_visit1
@@ -13,5 +13,6 @@
       "url": [ "https://example.com/file.txt" ]
     }
  ],
-  "version": 1
+  "version": 1,
+  "revision": "602140776b2ce6c9159bcf52ada73a297c063d5e"
 }
diff --git a/swh/loader/package/functional/tests/test_functional.py b/swh/loader/package/functional/tests/test_functional.py
--- a/swh/loader/package/functional/tests/test_functional.py
+++ b/swh/loader/package/functional/tests/test_functional.py
@@ -10,7 +10,7 @@
 )
 
 from swh.loader.package.tests.common import (
-    get_stats
+    get_stats, check_snapshot
 )
 
 sources_url = 'https://nix-community.github.io/nixpkgs-swh/sources.json'
@@ -101,3 +101,27 @@
     assert loader.resolve_revision_from(known_artifacts, metadata) == 'id1'
     metadata = {'url': 'url3'}
     assert loader.resolve_revision_from(known_artifacts, metadata) == None # noqa
+
+
+def test_evaluation_branch(swh_config, requests_mock_datadir):
+    loader = FunctionalLoader(sources_url, 'nixpkgs')
+    res = loader.load()
+    assert res['status'] == 'eventful'
+
+    expected_branches = {
+        'https://github.com/owner-1/repository-1/revision-1.tgz': {
+            'target': '488ad4e7b8e2511258725063cf43a2b897c503b4',
+            'target_type': 'revision',
+        },
+        'evaluation': {
+            'target': 'cc4e04c26672dd74e5fd0fecb78b435fb55368f7',
+            'target_type': 'revision',
+        },
+    }
+
+    expected_snapshot = {
+        'id': '0c5881c74283793ebe9a09a105a9381e41380383',
+        'branches': expected_branches,
+    }
+
+    check_snapshot(expected_snapshot, storage=loader.storage)
diff --git a/swh/loader/package/loader.py b/swh/loader/package/loader.py
--- a/swh/loader/package/loader.py
+++ b/swh/loader/package/loader.py
@@ -214,6 +214,15 @@
             uncompress(a_path, dest=uncompressed_path)
         return uncompressed_path
 
+    def hook_branches(
+            self, branches: Dict[bytes, Mapping[str, Any]]) \
+            -> Dict[bytes, Mapping[str, Any]]:
+        """This hook allows to modify the branches dict before creating the
+        snapshot.
+
+        """
+        return branches
+
     def load(self) -> Dict:
         """Load for a specific origin the associated contents.
 
@@ -326,7 +335,7 @@
                     }
 
             snapshot_data = {
-                'branches': branches
+                'branches': self.hook_branches(branches)
             }
             logger.debug('snapshot: %s', snapshot_data)