diff --git a/swh/search/elasticsearch.py b/swh/search/elasticsearch.py
--- a/swh/search/elasticsearch.py
+++ b/swh/search/elasticsearch.py
@@ -4,6 +4,7 @@
 # See top-level LICENSE file for more information
 
 import base64
+from textwrap import dedent
 from typing import Any, Dict, Iterable, Iterator, List, Optional
 
 from elasticsearch import Elasticsearch, helpers
@@ -168,22 +169,24 @@
             (origin_identifier(document), document) for document in documents
         )
         # painless script that will be executed when updating an origin document
-        update_script = """
-        // backup current visit_types field value
-        List visit_types = ctx._source.getOrDefault("visit_types", []);
-
-        // update origin document with new field values
-        ctx._source.putAll(params);
-
-        // restore previous visit types after visit_types field overriding
-        if (ctx._source.containsKey("visit_types")) {
-            for (int i = 0; i < visit_types.length; ++i) {
-                if (!ctx._source.visit_types.contains(visit_types[i])) {
-                    ctx._source.visit_types.add(visit_types[i]);
+        update_script = dedent(
+            """
+            // backup current visit_types field value
+            List visit_types = ctx._source.getOrDefault("visit_types", []);
+
+            // update origin document with new field values
+            ctx._source.putAll(params);
+
+            // restore previous visit types after visit_types field overriding
+            if (ctx._source.containsKey("visit_types")) {
+                for (int i = 0; i < visit_types.length; ++i) {
+                    if (!ctx._source.visit_types.contains(visit_types[i])) {
+                        ctx._source.visit_types.add(visit_types[i]);
+                    }
                 }
             }
-        }
-        """
+            """
+        )
 
         actions = [
             {
diff --git a/swh/search/tests/test_elasticsearch.py b/swh/search/tests/test_elasticsearch.py
--- a/swh/search/tests/test_elasticsearch.py
+++ b/swh/search/tests/test_elasticsearch.py
@@ -1,10 +1,13 @@
-# Copyright (C) 2019-2020  The Software Heritage developers
+# Copyright (C) 2019-2021  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
 
+from textwrap import dedent
+import types
 import unittest
 
+from elasticsearch.helpers.errors import BulkIndexError
 import pytest
 
 from swh.search.metrics import OPERATIONS_METRIC
@@ -19,6 +22,35 @@
         self.search = swh_search
         self.mocker = mocker
 
+        # override self.search.origin_update to catch painless script errors
+        # and pretty print them
+        origin_update = self.search.origin_update
+
+        def _origin_update(self, *args, **kwargs):
+            script_error = False
+            error_detail = ""
+            try:
+                origin_update(*args, **kwargs)
+            except BulkIndexError as e:
+                error = e.errors[0].get("update", {}).get("error", {}).get("caused_by")
+                if error and "script_stack" in error:
+                    script_error = True
+                    error_detail = dedent(
+                        f"""
+                        Painless update script failed ({error.get('reason')}).
+                        error type: {error.get('caused_by', {}).get('type')}
+                        error reason: {error.get('caused_by', {}).get('reason')}
+                        script stack:
+
+                        """
+                    )
+                    error_detail += "\n".join(error["script_stack"])
+                else:
+                    raise e
+            assert script_error is False, error_detail[1:]
+
+        self.search.origin_update = types.MethodType(_origin_update, self.search)
+
     def reset(self):
         self.search.deinitialize()
         self.search.initialize()