diff --git a/sql/upgrades/139.sql b/sql/upgrades/139.sql
new file mode 100644
--- /dev/null
+++ b/sql/upgrades/139.sql
@@ -0,0 +1,19 @@
+-- SWH DB schema upgrade
+-- from_version: 138
+-- to_version: 139
+-- description: Make fields target/name/perms of directory_entry_{dir,file,rev} not-null
+
+insert into dbversion(version, release, description)
+      values(139, now(), 'Work In Progress');
+
+alter table directory_entry_dir alter column target set not null;
+alter table directory_entry_dir alter column name set not null;
+alter table directory_entry_dir alter column perms set not null;
+
+alter table directory_entry_file alter column target set not null;
+alter table directory_entry_file alter column name set not null;
+alter table directory_entry_file alter column perms set not null;
+
+alter table directory_entry_rev alter column target set not null;
+alter table directory_entry_rev alter column name set not null;
+alter table directory_entry_rev alter column perms set not null;
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
@@ -17,7 +17,7 @@
 
 import attr
 
-from swh.model.model import Content
+from swh.model.model import Content, Directory
 from swh.model.hashutil import DEFAULT_ALGORITHMS
 from swh.model.identifiers import normalize_timestamp
 from swh.objstorage import get_objstorage
@@ -435,13 +435,15 @@
         if self.journal_writer:
             self.journal_writer.write_additions('directory', directories)
 
+        directories = [Directory.from_dict(d) for d in directories]
+
         count = 0
         for directory in directories:
-            if directory['id'] not in self._directories:
+            if directory.id not in self._directories:
                 count += 1
-                self._directories[directory['id']] = copy.deepcopy(directory)
-                self._objects[directory['id']].append(
-                    ('directory', directory['id']))
+                self._directories[directory.id] = directory
+                self._objects[directory.id].append(
+                    ('directory', directory.id))
 
         return {'directory:add': count}
 
@@ -480,8 +482,8 @@
 
     def _directory_ls(self, directory_id, recursive, prefix=b''):
         if directory_id in self._directories:
-            for entry in self._directories[directory_id]['entries']:
-                ret = self._join_dentry_to_content(entry)
+            for entry in self._directories[directory_id].entries:
+                ret = self._join_dentry_to_content(entry.to_dict())
                 ret['name'] = prefix + ret['name']
                 ret['dir_id'] = directory_id
                 yield ret
diff --git a/swh/storage/sql/30-swh-schema.sql b/swh/storage/sql/30-swh-schema.sql
--- a/swh/storage/sql/30-swh-schema.sql
+++ b/swh/storage/sql/30-swh-schema.sql
@@ -176,9 +176,9 @@
 create table directory_entry_dir
 (
   id      bigserial,
-  target  sha1_git,   -- id of target directory
-  name    unix_path,  -- path name, relative to containing dir
-  perms   file_perms  -- unix-like permissions
+  target  sha1_git not null,   -- id of target directory
+  name    unix_path not null,  -- path name, relative to containing dir
+  perms   file_perms not null  -- unix-like permissions
 );
 
 comment on table directory_entry_dir is 'Directory entry for directory';
@@ -192,9 +192,9 @@
 create table directory_entry_file
 (
   id      bigserial,
-  target  sha1_git,   -- id of target file
-  name    unix_path,  -- path name, relative to containing dir
-  perms   file_perms  -- unix-like permissions
+  target  sha1_git not null,   -- id of target file
+  name    unix_path not null,  -- path name, relative to containing dir
+  perms   file_perms not null  -- unix-like permissions
 );
 
 comment on table directory_entry_file is 'Directory entry for file';
@@ -208,9 +208,9 @@
 create table directory_entry_rev
 (
   id      bigserial,
-  target  sha1_git,   -- id of target revision
-  name    unix_path,  -- path name, relative to containing dir
-  perms   file_perms  -- unix-like permissions
+  target  sha1_git not null,   -- id of target revision
+  name    unix_path not null,  -- path name, relative to containing dir
+  perms   file_perms not null  -- unix-like permissions
 );
 
 comment on table directory_entry_rev is 'Directory entry for revision';
diff --git a/swh/storage/storage.py b/swh/storage/storage.py
--- a/swh/storage/storage.py
+++ b/swh/storage/storage.py
@@ -583,6 +583,10 @@
             for src_entry in cur_dir['entries']:
                 entry = src_entry.copy()
                 entry['dir_id'] = dir_id
+                if entry['type'] not in ('file', 'dir', 'rev'):
+                    raise ValueError(
+                        'Entry type must be file, dir, or rev; not %s'
+                        % entry['type'])
                 dir_entries[entry['type']][dir_id].append(entry)
 
         dirs_missing = set(self.directory_missing(dirs, db=db, cur=cur))
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
@@ -1010,6 +1010,20 @@
         after_missing = list(self.storage.directory_missing([self.dir['id']]))
         self.assertEqual([], after_missing)
 
+    def test_directory_add_validation(self):
+        dir_ = copy.deepcopy(self.dir)
+        dir_['entries'][0]['type'] = 'foobar'
+
+        with self.assertRaisesRegex(ValueError, 'type.*foobar'):
+            self.storage.directory_add([dir_])
+
+        dir_ = copy.deepcopy(self.dir)
+        del dir_['entries'][0]['target']
+
+        with self.assertRaisesRegex(
+                (TypeError, psycopg2.errors.NotNullViolation), 'target'):
+            self.storage.directory_add([dir_])
+
     def test_directory_get_recursive(self):
         init_missing = list(self.storage.directory_missing([self.dir['id']]))
         self.assertEqual([self.dir['id']], init_missing)