diff --git a/swh/loader/dir/tasks.py b/swh/loader/dir/tasks.py
index ad80749..d4c1c2e 100644
--- a/swh/loader/dir/tasks.py
+++ b/swh/loader/dir/tasks.py
@@ -1,102 +1,135 @@
 # Copyright (C) 2015  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import subprocess
 import shutil
 
 from swh.core.scheduling import Task
 from swh.core import config
 
 from swh.loader.dir.loader import DirLoader
 
 
 class LoadDirRepository(Task):
     """Import a directory to Software Heritage
 
     """
     task_queue = 'swh_loader_dir'
 
     CONFIG_BASE_FILENAME = 'loader/dir.ini'
     ADDITIONAL_CONFIG = {}
 
     def __init__(self):
         self.config = DirLoader.parse_config_file(
             base_filename=self.CONFIG_BASE_FILENAME,
             additional_configs=[self.ADDITIONAL_CONFIG],
         )
 
     def run(self, info):
         """Import a directory.
 
         Args:
             info: Dictionary of information needed, keys are:
               - dir_path: directory to import
               - origin_url: origin url (e.g file:///dev/null)
               - branch: occurrence's branch name
               - authority_id: authority id (e.g. 1 for swh)
               - validity: validity date (e.g. 2015-01-01 00:00:00+00)
               - revision_author_name: revision's author name
               - revision_author_email: revision's author email
               - revision_author_date: timestamp (e.g. 1444054085)
               - revision_author_offset: date offset e.g. -0220, +0100
               - revision_committer_name: revision's committer name
               - revision_committer_email: revision's committer email
               - revision_committer_date: timestamp
               - revision_committer_offset: date offset e.g. -0220, +0100
               - revision_type: type of revision dir, tar
               - revision_message: synthetic message for the revision
               - release_name: release name
               - release_date: release timestamp (e.g. 1444054085)
               - release_offset: release date offset e.g. -0220, +0100
               - release_author_name: release author's name
               - release_author_email: release author's email
               - release_comment: release's comment message
 
         """
         loader = DirLoader(self.config)
         loader.log = self.log
         loader.process(info)
 
 
 def untar(tar_path, dir_path):
     """Decompress an archive tar_path to dir_path.
 
     At the end of this call, dir_path contains the tarball's
     uncompressed content.
 
     Args:
         tar_path: the path to access the tarball
         dir_path: The path where to extract the tarball's content.
     """
     untar_cmd = ['tar', 'xavf', tar_path,
                  '--preserve-permissions',
                  '-C', dir_path]
     subprocess.check_call(untar_cmd, stderr=subprocess.STDOUT)
 
 
 class LoadTarRepository(LoadDirRepository):
     """Import a tarball to Software Heritage
 
     """
+    mandatory_keys = ['tar_path', 'dir_path',
+                      'authority_id', 'validity',
+                      'revision_author_name', 'revision_author_email',
+                      'revision_author_date', 'revision_author_offset',
+                      'revision_committer_name', 'revision_committer_email',
+                      'revision_committer_date', 'revision_committer_offset',
+                      'revision_type', 'revision_message',
+                      'release_name', 'release_date', 'release_offset',
+                      'release_author_name', 'release_author_email',
+                      'release_comment']
+
     task_queue = 'swh_loader_tar'
 
     CONFIG_BASE_FILENAME = 'loader/tar.ini'
     ADDITIONAL_CONFIG = {
         'dir_path': ('str', '/tmp/swh.loader.tar/'),
         'tar_path': ('str', '/some/path/to/tarball.tar')
     }
 
-    def run(self, info=None):
+    def check_for_missing_mandatory_data(self, info):
+        """Check for presence of mandatory information.
+
+        Args:
+            Dictionary of mandatory values.
+
+        Returns:
+            List of missing keys if any, an empty list otherwise.
+
+        Note:
+            Does not check the values, just that they are present.
+
+        """
+        missing_data = []
+        for key in self.mandatory_keys:
+            if key not in info:
+                missing_data.append(key)
+
+        return missing_data
+
+    def run(self, info):
         """Import a tarball.
 
         """
-        info = info if info else self.config
+        missing_data = self.check_for_missing_mandatory_data(info)
+        if not missing_data:
+            raise ValueError('%s are mandatory, failing!' % missing_data)
+
+        config.prepare_folders(info, 'dir_path')
         tar_path = info['tar_path']
         dir_path = info['dir_path']
-
-        config.prepare_folders(self.config, 'dir_path')
         untar(tar_path, dir_path)
         super().run(info)
         shutil.rmtree(dir_path)