diff --git a/swh/web/client/client.py b/swh/web/client/client.py
--- a/swh/web/client/client.py
+++ b/swh/web/client/client.py
@@ -28,6 +28,7 @@
 
 """
 
+from datetime import datetime
 from typing import Any, Callable, Dict, Iterator, List, Optional, Union
 from urllib.parse import urlparse
 
@@ -67,11 +68,16 @@
 
     """
 
-    def to_swhid(object_type, s):
+    def to_swhid(object_type: str, s: Any) -> SWHID:
         return SWHID(object_type=object_type, object_id=s)
 
-    def to_date(s):
-        return dateutil.parser.parse(s)
+    def to_date(date: str) -> datetime:
+        return dateutil.parser.parse(date)
+
+    def to_optional_date(date: Optional[str]) -> Optional[datetime]:
+        return None if date is None else to_date(date)
+
+    # The date attribute is optional for Revision and Release object
 
     def obj_type_of_entry_type(s):
         if s == "file":
@@ -92,12 +98,12 @@
         data["id"] = to_swhid(obj_type, data["id"])
         data["directory"] = to_swhid(DIRECTORY, data["directory"])
         for key in ("date", "committer_date"):
-            data[key] = to_date(data[key])
+            data[key] = to_optional_date(data[key])
         for parent in data["parents"]:
             parent["id"] = to_swhid(REVISION, parent["id"])
     elif obj_type == RELEASE:
         data["id"] = to_swhid(obj_type, data["id"])
-        data["date"] = to_date(data["date"])
+        data["date"] = to_optional_date(data["date"])
         data["target"] = to_swhid(data["target_type"], data["target"])
     elif obj_type == DIRECTORY:
         dir_swhid = None
diff --git a/swh/web/client/tests/test_web_api_client.py b/swh/web/client/tests/test_web_api_client.py
--- a/swh/web/client/tests/test_web_api_client.py
+++ b/swh/web/client/tests/test_web_api_client.py
@@ -7,7 +7,8 @@
 
 from dateutil.parser import parse as parse_date
 
-from swh.model.identifiers import parse_swhid
+from swh.model.identifiers import REVISION, parse_swhid
+from swh.web.client.client import typify_json
 
 from .api_data import API_DATA
 
@@ -172,3 +173,17 @@
                 break
 
         assert actual == expected
+
+
+def test_typify_json_minimal_revision():
+    revision_data = {
+        "id": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+        "directory": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+        "date": None,
+        "committer_date": None,
+        "parents": [],
+    }
+    revision_typed = typify_json(revision_data, REVISION)
+    pid = "swh:1:rev:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
+    assert revision_typed["id"] == parse_swhid(pid)
+    assert revision_typed["date"] is None