From ef88d3a9b614961baed72c1b5eacd8aec807a1d1 Mon Sep 17 00:00:00 2001
From: madlabman <10616301+madlabman@users.noreply.github.com>
Date: Thu, 4 Sep 2025 21:07:35 +0200
Subject: [PATCH] fix: do not check zero block root

---
 src/modules/csm/checkpoint.py | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/modules/csm/checkpoint.py b/src/modules/csm/checkpoint.py
index 0fb6573c1..cb1cead01 100644
--- a/src/modules/csm/checkpoint.py
+++ b/src/modules/csm/checkpoint.py
@@ -177,9 +177,12 @@ def _get_block_roots(self, checkpoint_slot: SlotNumber):
         pivot_index = checkpoint_slot % SLOTS_PER_HISTORICAL_ROOT
         # The oldest root can be missing, so we need to check it and mark it as well as other missing slots
         pivot_block_root = br[pivot_index]
-        slot_by_pivot_block_root = self.cc.get_block_header(pivot_block_root).data.header.message.slot
-        calculated_pivot_slot = max(checkpoint_slot - SLOTS_PER_HISTORICAL_ROOT, 0)
-        is_pivot_missing = slot_by_pivot_block_root != calculated_pivot_slot
+        if pivot_block_root == ZERO_BLOCK_ROOT:
+            is_pivot_missing = True
+        else:
+            slot_by_pivot_block_root = self.cc.get_block_header(pivot_block_root).data.header.message.slot
+            calculated_pivot_slot = max(checkpoint_slot - SLOTS_PER_HISTORICAL_ROOT, 0)
+            is_pivot_missing = slot_by_pivot_block_root != calculated_pivot_slot
 
         # Replace duplicated roots with `None` to mark missing slots
         br = [