diff --git a/swh/storage/in_memory.py b/swh/storage/in_memory.py
--- a/swh/storage/in_memory.py
+++ b/swh/storage/in_memory.py
@@ -14,7 +14,7 @@
 
 from collections import defaultdict
 from datetime import timedelta
-from typing import Any, Dict, List, Mapping, Optional
+from typing import Any, Dict, List, Optional
 
 import attr
 
@@ -1597,7 +1597,7 @@
             if random_origin_visits[0].type == type:
                 return url
 
-    def origin_visit_get_random(self, type: str) -> Mapping[str, Any]:
+    def origin_visit_get_random(self, type: str) -> Optional[Dict[str, Any]]:
         """Randomly select one successful origin visit with <type>
         made in the last 3 months.
 
@@ -1606,9 +1606,6 @@
             `origin_visit_get`.
 
         """
-        random_visit: Dict[str, Any] = {}
-        if not self._origin_visits:  # empty dataset
-            return random_visit
         url = self._select_random_origin_visit_by_type(type)
         random_origin_visits = copy.deepcopy(self._origin_visits[url])
         random_origin_visits.reverse()
@@ -1616,9 +1613,9 @@
         # This should be enough for tests
         for visit in random_origin_visits:
             if visit.date > back_in_the_day and visit.status == 'full':
-                random_visit = visit.to_dict()
-                break
-        return random_visit
+                return visit.to_dict()
+        else:
+            return None
 
     def stat_counters(self):
         """compute statistics about the number of tuples in various tables
diff --git a/swh/storage/storage.py b/swh/storage/storage.py
--- a/swh/storage/storage.py
+++ b/swh/storage/storage.py
@@ -11,7 +11,7 @@
 from collections import defaultdict
 from concurrent.futures import ThreadPoolExecutor
 from contextlib import contextmanager
-from typing import Any, Dict, List, Mapping, Optional
+from typing import Any, Dict, List, Optional
 
 import dateutil.parser
 import psycopg2
@@ -1610,7 +1610,7 @@
     @timed
     @db_transaction()
     def origin_visit_get_random(
-            self, type: str, db=None, cur=None) -> Mapping[str, Any]:
+            self, type: str, db=None, cur=None) -> Optional[Dict[str, Any]]:
         """Randomly select one successful origin visit with <type>
         made in the last 3 months.
 
@@ -1619,11 +1619,11 @@
             :py:meth:`origin_visit_get`.
 
         """
-        data: Dict[str, Any] = {}
         result = db.origin_visit_get_random(type, cur)
         if result:
-            data = dict(zip(db.origin_visit_get_cols, result))
-        return data
+            return dict(zip(db.origin_visit_get_cols, result))
+        else:
+            return None
 
     @remote_api_endpoint('object/find_by_sha1_git')
     @timed
diff --git a/swh/storage/tests/test_storage.py b/swh/storage/tests/test_storage.py
--- a/swh/storage/tests/test_storage.py
+++ b/swh/storage/tests/test_storage.py
@@ -1188,7 +1188,7 @@
                     origin['url'], visit_id=visit['visit'], status='full')
 
         random_origin_visit = swh_storage.origin_visit_get_random(visit_type)
-        assert random_origin_visit == {}
+        assert random_origin_visit is None
 
     def test_origin_get_by_sha1(self, swh_storage):
         assert swh_storage.origin_get(data.origin) is None