diff --git a/swh/vault/cookers/base.py b/swh/vault/cookers/base.py
--- a/swh/vault/cookers/base.py
+++ b/swh/vault/cookers/base.py
@@ -6,6 +6,7 @@
 import abc
 import io
 import logging
+import traceback
 from typing import ClassVar, Set
 
 from psycopg2.extensions import QueryCanceledError
@@ -141,10 +142,12 @@
             self.backend.set_progress(self.BUNDLE_TYPE, self.swhid, str(e))
         except Exception:
             self.backend.set_status(self.BUNDLE_TYPE, self.swhid, "failed")
+            tb = traceback.format_exc()
             self.backend.set_progress(
                 self.BUNDLE_TYPE,
                 self.swhid,
-                "Internal Server Error. This incident will be reported.",
+                f"Internal Server Error. This incident will be reported.\n"
+                f"The full error was:\n\n{tb}",
             )
             logging.exception("Bundle cooking failed.")
         else:
diff --git a/swh/vault/tests/test_cookers_base.py b/swh/vault/tests/test_cookers_base.py
--- a/swh/vault/tests/test_cookers_base.py
+++ b/swh/vault/tests/test_cookers_base.py
@@ -1,8 +1,9 @@
-# Copyright (C) 2018  The Software Heritage developers
+# Copyright (C) 2018-2021  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 textwrap
 from unittest.mock import MagicMock
 
 from swh.model.identifiers import CoreSWHID
@@ -56,7 +57,16 @@
     cooker.backend.put_bundle.assert_not_called()
 
     cooker.backend.set_status.assert_called_with(TEST_BUNDLE_TYPE, TEST_SWHID, "failed")
-    assert "Nope" not in cooker.backend.set_progress.call_args[0][2]
+    assert cooker.backend.set_progress.call_args[0][2].startswith(
+        textwrap.dedent(
+            """\
+            Internal Server Error. This incident will be reported.
+            The full error was:
+
+            Traceback (most recent call last):
+            """
+        )
+    )
     cooker.backend.send_notif.assert_called_with(TEST_BUNDLE_TYPE, TEST_SWHID)