diff --git a/swh/search/elasticsearch.py b/swh/search/elasticsearch.py
--- a/swh/search/elasticsearch.py
+++ b/swh/search/elasticsearch.py
@@ -120,6 +120,17 @@
         self._backend.indices.put_mapping(
             index=self._get_origin_index(),
             body={
+                "dynamic_templates": [
+                    {
+                        "booleans_as_string": {
+                            # All fields stored as string in the metadata
+                            # even the booleans
+                            "match_mapping_type": "boolean",
+                            "path_match": "intrinsic_metadata.*",
+                            "mapping": {"type": "keyword"},
+                        }
+                    }
+                ],
                 "date_detection": False,
                 "properties": {
                     # sha1 of the URL; used as the document id
diff --git a/swh/search/tests/test_search.py b/swh/search/tests/test_search.py
--- a/swh/search/tests/test_search.py
+++ b/swh/search/tests/test_search.py
@@ -501,7 +501,7 @@
         """Checks inserting a date-like in a field does not update the mapping to
         require every document uses a date in that field; or that search queries
         use a date either.
-        Likewise for numeric fields."""
+        Likewise for numeric and boolean fields."""
         origin1 = {"url": "http://origin1"}
         origin2 = {"url": "http://origin2"}
 
@@ -513,12 +513,12 @@
                         "@context": "https://doi.org/10.5063/schema/codemeta-2.0",
                         "dateCreated": "2021-02-18T10:16:52",
                         "version": "1.0",
+                        "isAccessibleForFree": True,
                     },
                 }
             ]
         )
         self.search.flush()
-
         self.search.origin_update(
             [
                 {
@@ -528,6 +528,7 @@
                         "dateCreated": "a long time ago",
                         "address": "in a galaxy far, far away",
                         "version": "a new hope",
+                        "isAccessibleForFree": "it depends",
                     },
                 },
             ]