diff --git a/include/bitcoin/system/chain/checkpoint.hpp b/include/bitcoin/system/chain/checkpoint.hpp
index 1befd7373c..ef8d4e5c18 100644
--- a/include/bitcoin/system/chain/checkpoint.hpp
+++ b/include/bitcoin/system/chain/checkpoint.hpp
@@ -103,8 +103,8 @@ bool operator==(const checkpoint& left, const checkpoint& right) NOEXCEPT;
 bool operator!=(const checkpoint& left, const checkpoint& right) NOEXCEPT;
 
 // TODO: rationalize with config.
+std::istream& operator>>(std::istream& stream, checkpoint& out) THROWS;
 std::ostream& operator<<(std::ostream& stream, const checkpoint& in) NOEXCEPT;
-std::istream& operator>>(std::istream& stream, checkpoint& out) NOEXCEPT;
 
 typedef std::vector<checkpoint> checkpoints;
 
diff --git a/include/bitcoin/system/error/block_error_t.hpp b/include/bitcoin/system/error/block_error_t.hpp
index cb5ee603fc..59dd0607f8 100644
--- a/include/bitcoin/system/error/block_error_t.hpp
+++ b/include/bitcoin/system/error/block_error_t.hpp
@@ -40,7 +40,7 @@ enum block_error_t : uint8_t
     // TODO: order these.
 
     // accept header
-    checkpoints_failed,
+    checkpoint_conflict,
     invalid_block_version,
     timestamp_too_early,
     incorrect_proof_of_work,
diff --git a/src/chain/block.cpp b/src/chain/block.cpp
index d9a3a23da0..30ecda77bc 100644
--- a/src/chain/block.cpp
+++ b/src/chain/block.cpp
@@ -705,7 +705,7 @@ code block::check(const context& ctx) const NOEXCEPT
     return check_transactions(ctx);
 }
 
-// These assume that prevout caching is completed on all inputs.
+// This assumes that prevout caching is completed on all inputs.
 code block::accept(const context& ctx, size_t subsidy_interval,
     uint64_t initial_subsidy) const NOEXCEPT
 {
@@ -722,7 +722,8 @@ code block::accept(const context& ctx, size_t subsidy_interval,
     return accept_transactions(ctx);
 }
 
-// This assume that prevout and metadata caching are completed on all inputs.
+// Node performs these checks through database query.
+// This assumes that prevout and metadata caching are completed on all inputs.
 code block::confirm(const context& ctx) const NOEXCEPT
 {
     const auto bip30 = ctx.is_enabled(bip30_rule);
diff --git a/src/chain/checkpoint.cpp b/src/chain/checkpoint.cpp
index e9958dc0a3..f5c093b697 100644
--- a/src/chain/checkpoint.cpp
+++ b/src/chain/checkpoint.cpp
@@ -133,25 +133,24 @@ bool operator!=(const checkpoint& left, const checkpoint& right) NOEXCEPT
 
 // TODO: add from_string.
 // TODO: add get_line/put_line to reader and eliminate stream_result.
-std::istream& operator>>(std::istream& stream, checkpoint& out) NOEXCEPT
+std::istream& operator>>(std::istream& stream, checkpoint& out) THROWS
 {
     std::string value;
     stream >> value;
 
     hash_digest hash;
     size_t height(zero);
-    const auto tokens = split(value, ":");
 
-    if (tokens.size() == two &&
-        decode_hash(hash, tokens.front()) &&
-        deserialize(height, tokens.back()))
-    {
-        out = { hash, height };
-        return stream_result(stream, true);
-    }
+    // std::string avoids boolean override.
+    const auto tokens = split(value, std::string{ ":" });
+
+    if (tokens.size() != two ||
+        !decode_hash(hash, tokens.front()) ||
+        !deserialize(height, tokens.back()))
+        throw istream_exception(value);
 
-    out = {};
-    return stream_result(stream, false);
+    out = { hash, height };
+    return stream;
 }
 
 bool checkpoint::is_valid() const NOEXCEPT
diff --git a/src/chain/transaction.cpp b/src/chain/transaction.cpp
index 061030472a..820994d9c3 100644
--- a/src/chain/transaction.cpp
+++ b/src/chain/transaction.cpp
@@ -1267,7 +1267,7 @@ code transaction::check(const context& ctx) const NOEXCEPT
 }
 
 // Do NOT invoke on coinbase.
-// These assume that prevout caching is completed on all inputs.
+// This assumes that prevout caching is completed on all inputs.
 code transaction::accept(const context&) const NOEXCEPT
 {
     BC_ASSERT(!is_coinbase());
diff --git a/src/error/block_error_t.cpp b/src/error/block_error_t.cpp
index 0a27da03fa..456ee9e6e5 100644
--- a/src/error/block_error_t.cpp
+++ b/src/error/block_error_t.cpp
@@ -34,7 +34,7 @@ DEFINE_ERROR_T_MESSAGE_MAP(block_error)
     { futuristic_timestamp, "timestamp too far in the future" },
 
     // accept header
-    { checkpoints_failed, "block hash rejected by checkpoint" },
+    { checkpoint_conflict, "block hash rejected by checkpoint" },
     { invalid_block_version, "block version rejected at current height" },
     { timestamp_too_early, "block timestamp is too early" },
     { incorrect_proof_of_work, "proof of work does not match bits field" },
diff --git a/test/error/block_error_t.cpp b/test/error/block_error_t.cpp
index b2c8da5714..e6f9fffb8f 100644
--- a/test/error/block_error_t.cpp
+++ b/test/error/block_error_t.cpp
@@ -53,9 +53,9 @@ BOOST_AUTO_TEST_CASE(block_error_t__code__futuristic_timestamp__true_exected_mes
 
 // accept header
 
-BOOST_AUTO_TEST_CASE(block_error_t__code__checkpoints_failed__true_exected_message)
+BOOST_AUTO_TEST_CASE(block_error_t__code__checkpoint_conflict__true_exected_message)
 {
-    constexpr auto value = error::checkpoints_failed;
+    constexpr auto value = error::checkpoint_conflict;
     const auto ec = code(value);
     BOOST_REQUIRE(ec);
     BOOST_REQUIRE(ec == value);