diff --git a/include/bitcoin/system/chain/block.hpp b/include/bitcoin/system/chain/block.hpp
index c63d689c85..96491f210a 100644
--- a/include/bitcoin/system/chain/block.hpp
+++ b/include/bitcoin/system/chain/block.hpp
@@ -104,9 +104,11 @@ class BC_API block
 
     /// Computed malleation properties.
     bool is_malleable() const NOEXCEPT;
-    bool is_malleable64() const NOEXCEPT;
+    bool is_malleated() const NOEXCEPT;
     bool is_malleable32() const NOEXCEPT;
     bool is_malleated32() const NOEXCEPT;
+    bool is_malleable64() const NOEXCEPT;
+    bool is_malleated64() const NOEXCEPT;
 
     /// Validation.
     /// -----------------------------------------------------------------------
diff --git a/include/bitcoin/system/error/block_error_t.hpp b/include/bitcoin/system/error/block_error_t.hpp
index b9ea622996..ae271faf4a 100644
--- a/include/bitcoin/system/error/block_error_t.hpp
+++ b/include/bitcoin/system/error/block_error_t.hpp
@@ -56,7 +56,7 @@ enum block_error_t : uint8_t
     forward_reference,
     invalid_transaction_commitment,
     block_legacy_sigop_limit,
-    type32_malleated,
+    block_malleated,
 
     // accept block
     block_non_final,
diff --git a/src/chain/block.cpp b/src/chain/block.cpp
index c6d9bceeea..b945141206 100644
--- a/src/chain/block.cpp
+++ b/src/chain/block.cpp
@@ -452,6 +452,11 @@ bool block::is_malleable() const NOEXCEPT
     return is_malleable64() || is_malleable32();
 }
 
+bool block::is_malleated() const NOEXCEPT
+{
+    return is_malleated32() || is_malleated64();
+}
+
 bool block::is_malleable32() const NOEXCEPT
 {
     const auto unmalleated = txs_->size();
@@ -514,6 +519,14 @@ bool block::is_malleable64(const transaction_cptrs& txs) NOEXCEPT
     return !txs.empty() && std::all_of(txs.begin(), txs.end(), two_leaves);
 }
 
+// A mallaeable64 block is considered malleated if the first tx is not a valid
+// coinbase. It is possible but computationally infeasible to grind a valid
+// coinbase and therefore treated similarly to sha256 hash collision.
+bool block::is_malleated64() const NOEXCEPT
+{
+    return is_malleable64(*txs_) && !txs_->front()->is_coinbase();
+}
+
 bool block::is_segregated() const NOEXCEPT
 {
     const auto segregated = [](const auto& tx) NOEXCEPT
@@ -736,9 +749,10 @@ code block::check(bool bypass) const NOEXCEPT
     if (is_invalid_merkle_root())
         return error::invalid_transaction_commitment;
 
-    // type32_malleated is subset of is_internal_double_spend
-    if (bypass && is_malleated32())
-        return error::type32_malleated;
+    // type32 malleated is a subset of is_internal_double_spend
+    // type64 malleated is a subset of first_not_coinbase
+    if (bypass && is_malleated())
+        return error::block_malleated;
     if (bypass)
         return error::block_success;
 
diff --git a/src/error/block_error_t.cpp b/src/error/block_error_t.cpp
index ca63b5d4ff..6475a85ee0 100644
--- a/src/error/block_error_t.cpp
+++ b/src/error/block_error_t.cpp
@@ -52,7 +52,7 @@ DEFINE_ERROR_T_MESSAGE_MAP(block_error)
     { forward_reference, "transactions out of order" },
     { invalid_transaction_commitment, "invalid transaction commitment" },
     { block_legacy_sigop_limit, "too many block legacy signature operations" },
-    { type32_malleated, "block is type32 malleated" },
+    { block_malleated, "block is malleated" },
 
     // accept block
     { block_non_final, "block contains a non-final transaction" },
diff --git a/test/error/block_error_t.cpp b/test/error/block_error_t.cpp
index 6f4f7a72b4..47399379d0 100644
--- a/test/error/block_error_t.cpp
+++ b/test/error/block_error_t.cpp
@@ -183,13 +183,13 @@ BOOST_AUTO_TEST_CASE(block_error_t__code__block_legacy_sigop_limit__true_exected
     BOOST_REQUIRE_EQUAL(ec.message(), "too many block legacy signature operations");
 }
 
-BOOST_AUTO_TEST_CASE(block_error_t__code__type32_malleated__true_exected_message)
+BOOST_AUTO_TEST_CASE(block_error_t__code__block_malleated__true_exected_message)
 {
-    constexpr auto value = error::type32_malleated;
+    constexpr auto value = error::block_malleated;
     const auto ec = code(value);
     BOOST_REQUIRE(ec);
     BOOST_REQUIRE(ec == value);
-    BOOST_REQUIRE_EQUAL(ec.message(), "block is type32 malleated");
+    BOOST_REQUIRE_EQUAL(ec.message(), "block is malleated");
 }
 
 // accept block