diff --git a/include/bitcoin/system/impl/stream/streamers/hex_writer.ipp b/include/bitcoin/system/impl/stream/streamers/hex_writer.ipp
index 8053008279..f88843ea7b 100644
--- a/include/bitcoin/system/impl/stream/streamers/hex_writer.ipp
+++ b/include/bitcoin/system/impl/stream/streamers/hex_writer.ipp
@@ -52,7 +52,6 @@ template <typename OStream>
 void hex_writer<OStream>::do_write_bytes(const uint8_t* data,
     size_t size) NOEXCEPT
 {
-    BC_ASSERT(!is_null(data));
     BC_ASSERT(!is_multiply_overflow(size, octet_width));
 
     char chars[octet_width]{};
diff --git a/src/chain/block.cpp b/src/chain/block.cpp
index a6ea38bca1..367e5bfdb7 100644
--- a/src/chain/block.cpp
+++ b/src/chain/block.cpp
@@ -671,13 +671,17 @@ static uint64_t block_subsidy(size_t height, uint64_t subsidy_interval,
 
 uint64_t block::fees() const NOEXCEPT
 {
+    if (txs_->empty())
+        return {};
+
     // Overflow returns max_uint64.
     const auto value = [](uint64_t total, const auto& tx) NOEXCEPT
     {
         return ceilinged_add(total, tx->fee());
     };
 
-    return std::accumulate(txs_->begin(), txs_->end(), uint64_t{}, value);
+    return std::accumulate(std::next(txs_->begin()), txs_->end(),
+        uint64_t{}, value);
 }
 
 uint64_t block::claim() const NOEXCEPT
diff --git a/src/chain/header.cpp b/src/chain/header.cpp
index 16d7d9d340..725a204cbb 100644
--- a/src/chain/header.cpp
+++ b/src/chain/header.cpp
@@ -386,7 +386,7 @@ DEFINE_JSON_FROM_TAG(header)
 {
     value =
     {
-        // hash is meta property
+        // hash is computed property
         { "hash", encode_hash(instance.hash()) },
         { "version", instance.version() },
         { "previous", encode_hash(instance.previous_block_hash()) },
diff --git a/src/chain/transaction.cpp b/src/chain/transaction.cpp
index e244a4dadf..19cd5601e2 100644
--- a/src/chain/transaction.cpp
+++ b/src/chain/transaction.cpp
@@ -969,7 +969,7 @@ DEFINE_JSON_FROM_TAG(transaction)
 {
     value =
     {
-        // hash is meta property
+        // hash is computed property
         { "hash", encode_hash(instance.hash(false)) },
         { "version", instance.version() },
         { "inputs", value_from(*instance.inputs_ptr()) },