diff --git a/swh/web/common/service.py b/swh/web/common/service.py
--- a/swh/web/common/service.py
+++ b/swh/web/common/service.py
@@ -1046,12 +1046,22 @@
         A dict filled with the snapshot content.
     """
     snapshot_id_bin = _to_sha1_bin(snapshot_id)
+    # not actually a snapshot, it's a dict with branches and a "next_branch" value.
     snapshot = storage.snapshot_get_branches(
         snapshot_id_bin, branches_from.encode(), branches_count, target_types
     )
     if not snapshot:
         raise NotFoundExc("Snapshot with id %s not found!" % snapshot_id)
-    return converters.from_snapshot(snapshot)
+    return converters.from_snapshot(
+        {
+            "id": snapshot["id"],
+            "branches": {
+                branch_name: branch.to_dict() if branch else None
+                for (branch_name, branch) in snapshot["branches"].items()
+            },
+            "next_branch": snapshot["next_branch"],
+        }
+    )
 
 
 def lookup_latest_origin_snapshot(
diff --git a/swh/web/tests/conftest.py b/swh/web/tests/conftest.py
--- a/swh/web/tests/conftest.py
+++ b/swh/web/tests/conftest.py
@@ -298,7 +298,16 @@
             branches_count,
             target_types,
         )
-        return converters.from_snapshot(snp)
+        return converters.from_snapshot(
+            {
+                "id": snp["id"],
+                "branches": {
+                    branch_name: branch.to_dict()
+                    for (branch_name, branch) in snp["branches"].items()
+                },
+                "next_branch": None,
+            }
+        )
 
     def snapshot_get_head(self, snapshot):
         if snapshot["branches"]["HEAD"]["target_type"] == "alias":