diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index cd5b4f455..206d5fbb9 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -4749,6 +4749,8 @@ uint64_t Blockchain::prevalidate_block_hashes(uint64_t height, const std::vector
 
   CHECK_AND_ASSERT_MES(weights.empty() || weights.size() == hashes.size(), 0, "Unexpected weights size");
 
+  CRITICAL_REGION_LOCAL(m_blockchain_lock);
+
   // easy case: height >= hashes
   if (height >= m_blocks_hash_of_hashes.size() * HASH_OF_HASHES_STEP)
     return hashes.size();