diff --git a/swh/scanner/benchmark_algos.py b/swh/scanner/benchmark_algos.py
--- a/swh/scanner/benchmark_algos.py
+++ b/swh/scanner/benchmark_algos.py
@@ -254,6 +254,7 @@
 
     for node in all_nodes:
         if node.otype == CONTENT and not node.known:
+            all_nodes_copy.remove(node)
             remove_parents(node, all_nodes_copy)
 
     for node in all_nodes_copy: