diff --git a/requirements-swh.txt b/requirements-swh.txt
--- a/requirements-swh.txt
+++ b/requirements-swh.txt
@@ -2,4 +2,4 @@
 swh.model >= 1.0.0
 swh.objstorage >= 0.2.2
 swh.scheduler >= 0.4.0
-swh.storage >= 0.13.1
+swh.storage >= 0.27.0
diff --git a/swh/loader/package/loader.py b/swh/loader/package/loader.py
--- a/swh/loader/package/loader.py
+++ b/swh/loader/package/loader.py
@@ -44,6 +44,7 @@
     ObjectType,
 )
 from swh.model.model import (
+    ExtID,
     MetadataAuthority,
     MetadataAuthorityType,
     MetadataFetcher,
@@ -588,6 +589,7 @@
                 branch.target for branch in last_snapshot.branches.values()
             }
 
+        new_extids: Set[ExtID] = set()
         tmp_revisions: Dict[str, List[Tuple[str, Sha1Git]]] = {
             version: [] for version in versions
         }
@@ -633,6 +635,16 @@
                 if revision_id is None:
                     continue
 
+                partial_extid = p_info.extid()
+                if partial_extid is not None:
+                    (extid_type, extid) = partial_extid
+                    revision_swhid = CoreSWHID(
+                        object_type=ObjectType.REVISION, object_id=revision_id
+                    )
+                    new_extids.add(
+                        ExtID(extid_type=extid_type, extid=extid, target=revision_swhid)
+                    )
+
             tmp_revisions[version].append((branch_name, revision_id))
 
         if load_exceptions:
@@ -689,6 +701,8 @@
             status_visit = "partial"
             status_load = "failed"
 
+        self._load_extids(new_extids)
+
         return self.finalize_visit(
             snapshot=snapshot,
             visit=visit,
@@ -1001,3 +1015,14 @@
         }
         if fetchers:
             self.storage.metadata_fetcher_add(list(deduplicated_fetchers.values()))
+
+    def _load_extids(self, extids: Set[ExtID]) -> None:
+        if not extids:
+            return
+        try:
+            self.storage.extid_add(list(extids))
+        except Exception as e:
+            logger.exception("Failed to load new ExtIDs for %s", self.url)
+            sentry_sdk.capture_exception(e)
+            # No big deal, it just means the next visit will load the same versions
+            # again.
diff --git a/swh/loader/package/nixguix/tests/test_nixguix.py b/swh/loader/package/nixguix/tests/test_nixguix.py
--- a/swh/loader/package/nixguix/tests/test_nixguix.py
+++ b/swh/loader/package/nixguix/tests/test_nixguix.py
@@ -697,10 +697,10 @@
 
         expected_detections = [
             {"reason": "'integrity'", "known_artifact": old_revision.metadata,},
-            {"reason": "'integrity'", "known_artifact": old_revision.metadata,},
         ]
 
-        # as many calls as there are sources listed in the sources.json
-        assert len(expected_detections) == len(all_sources["sources"])
+        # less calls than there are sources listed in the sources.json;
+        # as some of them are skipped using the ExtID from a previous run
+        assert len(expected_detections) <= len(all_sources["sources"])
 
         assert actual_detections == expected_detections
diff --git a/swh/loader/package/tests/test_loader.py b/swh/loader/package/tests/test_loader.py
--- a/swh/loader/package/tests/test_loader.py
+++ b/swh/loader/package/tests/test_loader.py
@@ -202,8 +202,9 @@
     )
 
 
-def test_load_skip_extids() -> None:
-    """Checks PackageLoader.load() skips iff it should."""
+def test_load_extids() -> None:
+    """Checks PackageLoader.load() skips iff it should, and writes (only)
+    the new ExtIDs"""
     storage = get_storage("memory")
 
     origin = "http://example.org"
@@ -295,6 +296,26 @@
     )
     assert snapshot_get_latest(storage, origin) == snapshot
 
+    extids = storage.extid_get_from_target(
+        ObjectType.REVISION,
+        [
+            rev1_swhid.object_id,
+            rev2_swhid.object_id,
+            rev3_swhid.object_id,
+            rev4_swhid.object_id,
+        ],
+    )
+
+    assert set(extids) == {
+        # What we inserted at the beginning of the test:
+        ExtID("extid-type1", b"extid-of-v1.0", rev1_swhid),
+        ExtID("extid-type2", b"extid-of-v2.0", rev2_swhid),
+        # Added by the loader:
+        ExtID("extid-type1", b"extid-of-v2.0", rev4_swhid),
+        ExtID("extid-type2", b"extid-of-v3.0", rev4_swhid),
+        ExtID("extid-type2", b"extid-of-v4.0", rev4_swhid),
+    }
+
 
 def test_manifest_extid():
     """Compute primary key should return the right identity