diff --git a/src/blockencodings.cpp b/src/blockencodings.cpp
index c27cde2162f59..48431cfb3c7b5 100644
--- a/src/blockencodings.cpp
+++ b/src/blockencodings.cpp
@@ -47,7 +47,7 @@ uint64_t CBlockHeaderAndShortTxIDs::GetShortID(const uint256& txhash) const {
 
 
 
-ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, std::vector<std::pair<uint256, CTransactionRef>>& extra_txn) {
+ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, const std::vector<std::pair<uint256, CTransactionRef>>& extra_txn) {
     if (cmpctblock.header.IsNull() || (cmpctblock.shorttxids.empty() && cmpctblock.prefilledtxn.empty()))
         return READ_STATUS_INVALID;
     if (cmpctblock.shorttxids.size() + cmpctblock.prefilledtxn.size() > MAX_BLOCK_BASE_SIZE / MIN_TRANSACTION_BASE_SIZE)
diff --git a/src/blockencodings.h b/src/blockencodings.h
index 971476cbbdaef..281db9fe01f32 100644
--- a/src/blockencodings.h
+++ b/src/blockencodings.h
@@ -201,7 +201,7 @@ class PartiallyDownloadedBlock {
     PartiallyDownloadedBlock(CTxMemPool* poolIn) : pool(poolIn) {}
 
     // extra_txn is a list of extra transactions to look at, in <witness hash, reference> form
-    ReadStatus InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, std::vector<std::pair<uint256, CTransactionRef>>& extra_txn);
+    ReadStatus InitData(const CBlockHeaderAndShortTxIDs& cmpctblock, const std::vector<std::pair<uint256, CTransactionRef>>& extra_txn);
     bool IsTxAvailable(size_t index) const;
     ReadStatus FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing);
 };