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
@@ -812,7 +812,7 @@
             raise ValueError('Origin must have either id or (type and url).')
         origin = None
         # self._origin_id can return None
-        if origin_id is not None:
+        if origin_id is not None and origin_id <= len(self._origins):
             origin = copy.deepcopy(self._origins[origin_id-1])
             origin['id'] = origin_id
         return origin
@@ -1017,14 +1017,15 @@
             List of visits.
 
         """
-        visits = self._origin_visits[origin-1]
-        if last_visit is not None:
-            visits = visits[last_visit:]
-        if limit is not None:
-            visits = visits[:limit]
-        for visit in visits:
-            visit_id = visit['visit']
-            yield copy.deepcopy(self._origin_visits[origin-1][visit_id-1])
+        if origin <= len(self._origin_visits):
+            visits = self._origin_visits[origin-1]
+            if last_visit is not None:
+                visits = visits[last_visit:]
+            if limit is not None:
+                visits = visits[:limit]
+            for visit in visits:
+                visit_id = visit['visit']
+                yield copy.deepcopy(self._origin_visits[origin-1][visit_id-1])
 
     def origin_visit_get_by(self, origin, visit):
         """Retrieve origin visit's information.
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
@@ -2139,6 +2139,16 @@
 
                                 keys_to_check)
 
+    def test_origin_get_ko(self):
+
+        invalid_origin_id = 1
+
+        origin_info = self.storage.origin_get({'id': invalid_origin_id})
+        self.assertIsNone(origin_info)
+
+        origin_visits = list(self.storage.origin_visit_get(invalid_origin_id))
+        self.assertEqual(origin_visits, [])
+
     @given(gen_origins(min_size=100, max_size=100))
     def test_origin_get_range(self, new_origins):