diff --git a/swh/graph/luigi/misc_datasets.py b/swh/graph/luigi/misc_datasets.py
--- a/swh/graph/luigi/misc_datasets.py
+++ b/swh/graph/luigi/misc_datasets.py
@@ -39,7 +39,7 @@
 import luigi
 
 from .compressed_graph import LocalGraph
-from .utils import run_script
+from .utils import run_script, silence_webgraph_cache_warning
 
 
 class TopoSort(luigi.Task):
@@ -62,6 +62,7 @@
         """Runs org.softwareheritage.graph.utils.TopoSort and compresses"""
         object_types = "rev,rel,snp,ori"
         class_name = "org.softwareheritage.graph.utils.TopoSort"
+        silence_webgraph_cache_warning(self.local_graph_path)
         script = f"""
         java {class_name} '{self.local_graph_path}/{self.graph_name}' '{object_types}' \
             | pv --line-mode --wait \
diff --git a/swh/graph/luigi/origin_contributors.py b/swh/graph/luigi/origin_contributors.py
--- a/swh/graph/luigi/origin_contributors.py
+++ b/swh/graph/luigi/origin_contributors.py
@@ -20,7 +20,7 @@
 
 from .compressed_graph import LocalGraph
 from .misc_datasets import TopoSort
-from .utils import run_script
+from .utils import run_script, silence_webgraph_cache_warning
 
 
 class ListOriginContributors(luigi.Task):
@@ -51,6 +51,7 @@
     def run(self) -> None:
         """Runs org.softwareheritage.graph.utils.TopoSort and compresses"""
         class_name = "org.softwareheritage.graph.utils.ListOriginContributors"
+        silence_webgraph_cache_warning(self.local_graph_path)
         script = f"""
         zstdcat {self.topological_order_path} \
             | java {class_name} '{self.local_graph_path}/{self.graph_name}' \
diff --git a/swh/graph/luigi/utils.py b/swh/graph/luigi/utils.py
--- a/swh/graph/luigi/utils.py
+++ b/swh/graph/luigi/utils.py
@@ -33,3 +33,13 @@
 
     # Atomically write the output file
     tmp_output_path.replace(output_path)
+
+
+def silence_webgraph_cache_warning(local_graph_path: Path):
+    """Touches .obl files so WebGraph does not warn about them being older than
+    .offset files.
+
+    This workaround is a workaround for https://github.com/vigna/webgraph-big/pull/6
+    """
+    for path in local_graph_path.glob("*.obl"):
+        path.touch()