diff --git a/swh/loader/mercurial/from_disk.py b/swh/loader/mercurial/from_disk.py
--- a/swh/loader/mercurial/from_disk.py
+++ b/swh/loader/mercurial/from_disk.py
@@ -289,6 +289,25 @@
             ]
         return extids
 
+    def _get_extids_for_hgnodes(self, hgnode_ids: List[bytes]) -> List[ExtID]:
+        """Get all Mercurial ExtIDs for the mercurial nodes in the list."""
+        extids = [
+            extid
+            for extid in self.storage.extid_get_from_extid(EXTID_TYPE, hgnode_ids)
+            if extid.extid_version == EXTID_VERSION
+        ]
+        if extids:
+            # Filter out dangling extids, we need to load their target again
+            revisions_missing = self.storage.revision_missing(
+                [extid.target.object_id for extid in extids]
+            )
+            extids = [
+                extid
+                for extid in extids
+                if extid.target.object_id not in revisions_missing
+            ]
+        return extids
+
     def fetch_data(self) -> bool:
         """Fetch the data from the source the loader is currently loading
 
@@ -317,28 +336,45 @@
 
         return False
 
+    def _new_revs(self, heads: List[bytes]):
+        """Return unseen revisions. That is, filter out revisions that are not ancestors of
+        heads"""
+        assert self._repo is not None
+        existing_heads = []
+
+        for hg_nodeid in heads:
+            try:
+                rev = self._repo[hg_nodeid].rev()
+                existing_heads.append(rev)
+            except KeyError:  # the node does not exist anymore
+                pass
+
+        # select revisions that are not ancestors of heads
+        # and not the heads themselves
+        new_revs = self._repo.revs("not ::(%ld)", existing_heads)
+
+        if new_revs:
+            self.log.info("New revisions found: %d", len(new_revs))
+
+        return new_revs
+
     def get_hg_revs_to_load(self) -> Union[HgFilteredSet, HgSpanSet]:
         """Return the hg revision numbers to load."""
         assert self._repo is not None
         repo: hgutil.Repository = self._repo
+
         if self._latest_heads:
-            existing_heads = []  # heads that still exist in the repository
-            for hg_nodeid in self._latest_heads:
-                try:
-                    rev = repo[hg_nodeid].rev()
-                    existing_heads.append(rev)
-                except KeyError:  # the node does not exist anymore
-                    pass
-
-            # select revisions that are not ancestors of heads
-            # and not the heads themselves
-            new_revs = repo.revs("not ::(%ld)", existing_heads)
-
-            if new_revs:
-                self.log.info("New revisions found: %d", len(new_revs))
-            return new_revs
+            # Reuse existing seen heads from last snapshot
+            new_revs = self._new_revs(self._latest_heads)
         else:
-            return repo.revs("all()")
+            # otherwise, try to filter out across origins already seen revisions
+            all_revs = repo.revs("all()")
+            hg_nodeids = [repo[nodeid].node() for nodeid in all_revs]
+            new_revs = self._new_revs(
+                [extid.extid for extid in self._get_extids_for_hgnodes(hg_nodeids)]
+            )
+
+        return new_revs
 
     def store_data(self):
         """Store fetched data in the database."""
@@ -422,6 +458,7 @@
             snapshot_branches[b"HEAD"] = SnapshotBranch(
                 target=default_branch_alias, target_type=TargetType.ALIAS,
             )
+
         snapshot = Snapshot(branches=snapshot_branches)
         self.storage.snapshot_add([snapshot])
 
diff --git a/swh/loader/mercurial/tests/test_from_disk.py b/swh/loader/mercurial/tests/test_from_disk.py
--- a/swh/loader/mercurial/tests/test_from_disk.py
+++ b/swh/loader/mercurial/tests/test_from_disk.py
@@ -164,7 +164,7 @@
     check_snapshot(expected_snapshot, loader.storage)
 
     stats = get_stats(loader.storage)
-    assert stats == {
+    expected_stats = {
         "content": 2,
         "directory": 3,
         "origin": 1,
@@ -175,6 +175,19 @@
         "snapshot": 1,
     }
 
+    assert stats == expected_stats
+    loader2 = HgLoaderFromDisk(swh_storage, url=repo_url)
+
+    assert loader2.load() == {"status": "uneventful"}
+
+    stats2 = get_stats(loader2.storage)
+    expected_stats2 = expected_stats.copy()
+    expected_stats2.update(
+        {"origin_visit": 1 + 1,}
+    )
+    assert stats2 == expected_stats2
+    # FIXME: Already seen objects are filtered out, so no new snapshot.
+
 
 # This test has as been adapted from the historical `HgBundle20Loader` tests
 # to ensure compatibility of `HgLoaderFromDisk`.