diff --git a/swh/model/from_disk.py b/swh/model/from_disk.py
--- a/swh/model/from_disk.py
+++ b/swh/model/from_disk.py
@@ -549,6 +549,13 @@
             key1, key2 = key.rsplit(b"/", 1)
             del self[key1][key2]
 
+    def __contains__(self, key):
+        if b"/" not in key:
+            return super().__contains__(key)
+        else:
+            key1, key2 = key.split(b"/", 1)
+            return super().__contains__(key1) and self[key1].__contains__(key2)
+
     def __repr__(self):
         return "Directory(id=%s, entries=[%s])" % (
             hash_to_hex(self.hash),
diff --git a/swh/model/tests/test_from_disk.py b/swh/model/tests/test_from_disk.py
--- a/swh/model/tests/test_from_disk.py
+++ b/swh/model/tests/test_from_disk.py
@@ -978,3 +978,19 @@
             del d["foo"]
         with self.assertRaisesRegex(ValueError, "bytes Directory entry"):
             del d[42]
+
+    def test_directory_contains(self):
+        d = Directory()
+        d[b"a"] = Directory()
+        d[b"a/b"] = Directory()
+        d[b"a/b/c"] = Directory()
+        d[b"a/b/c/d"] = Content()
+
+        self.assertIn(b"a", d)
+        self.assertIn(b"a/b", d)
+        self.assertIn(b"a/b/c", d)
+        self.assertIn(b"a/b/c/d", d)
+
+        self.assertNotIn(b"b", d)
+        self.assertNotIn(b"b/c", d)
+        self.assertNotIn(b"b/c/d", d)