diff --git a/src/p2p_server.cpp b/src/p2p_server.cpp
index c9ec1df..7679d5d 100644
--- a/src/p2p_server.cpp
+++ b/src/p2p_server.cpp
@@ -3813,8 +3813,8 @@ bool P2PServer::P2PClient::on_monero_block_broadcast(const uint8_t* buf, uint32_
 					if (p && p > p_start) {
 						const size_t old_ptx_size = static_cast<size_t>(p - p_start);
 						LOGINFO(1, "P2P submit: splicing real protocol_tx (" << mdata.protocol_tx_blob.size() << " bytes) at offset " << ptx_offset);
-						block_blob.erase(block_blob.begin() + ptx_offset, block_blob.begin() + ptx_offset + old_ptx_size);
-						block_blob.insert(block_blob.begin() + ptx_offset, mdata.protocol_tx_blob.begin(), mdata.protocol_tx_blob.end());
+						block_blob.erase(block_blob.begin() + static_cast<ptrdiff_t>(ptx_offset), block_blob.begin() + static_cast<ptrdiff_t>(ptx_offset + old_ptx_size));
+						block_blob.insert(block_blob.begin() + static_cast<ptrdiff_t>(ptx_offset), mdata.protocol_tx_blob.begin(), mdata.protocol_tx_blob.end());
 					}
 				}
 
diff --git a/src/p2pool.cpp b/src/p2pool.cpp
index 03868ef..c041262 100644
--- a/src/p2pool.cpp
+++ b/src/p2pool.cpp
@@ -1188,8 +1188,8 @@ void p2pool::submit_block() const
 		MinerData data = miner_data();
 		if (!data.protocol_tx_blob.empty() && data.protocol_tx_loaded && ptx_offset > 0 && ptx_size > 0) {
 			LOGINFO(1, "submit_block: splicing real protocol_tx (" << data.protocol_tx_blob.size() << " bytes) at offset " << ptx_offset);
-			submit_data.blob.erase(submit_data.blob.begin() + ptx_offset, submit_data.blob.begin() + ptx_offset + ptx_size);
-			submit_data.blob.insert(submit_data.blob.begin() + ptx_offset, data.protocol_tx_blob.begin(), data.protocol_tx_blob.end());
+			submit_data.blob.erase(submit_data.blob.begin() + static_cast<ptrdiff_t>(ptx_offset), submit_data.blob.begin() + static_cast<ptrdiff_t>(ptx_offset + ptx_size));
+			submit_data.blob.insert(submit_data.blob.begin() + static_cast<ptrdiff_t>(ptx_offset), data.protocol_tx_blob.begin(), data.protocol_tx_blob.end());
 		}
         }
         else {