diff --git a/lib/evmone/instructions.hpp b/lib/evmone/instructions.hpp
index 19772a4bb7..f6598da8c2 100644
--- a/lib/evmone/instructions.hpp
+++ b/lib/evmone/instructions.hpp
@@ -906,6 +906,11 @@ inline evmc_status_code dataload(StackTop stack, ExecutionState& state) noexcept
     return EVMC_SUCCESS;
 }
 
+inline void datasize(StackTop stack, ExecutionState& state) noexcept
+{
+    stack.push(state.data.size());
+}
+
 template <size_t NumTopics>
 inline evmc_status_code log(StackTop stack, ExecutionState& state) noexcept
 {
diff --git a/lib/evmone/instructions_opcodes.hpp b/lib/evmone/instructions_opcodes.hpp
index 7dfee579a4..614bce7531 100644
--- a/lib/evmone/instructions_opcodes.hpp
+++ b/lib/evmone/instructions_opcodes.hpp
@@ -164,6 +164,7 @@ enum Opcode : uint8_t
     OP_SWAPN = 0xb6,
 
     OP_DATALOAD = 0xb7,
+    OP_DATASIZE = 0xb8,
 
     OP_CREATE = 0xf0,
     OP_CALL = 0xf1,
diff --git a/lib/evmone/instructions_traits.hpp b/lib/evmone/instructions_traits.hpp
index 428b22d7eb..78ec994312 100644
--- a/lib/evmone/instructions_traits.hpp
+++ b/lib/evmone/instructions_traits.hpp
@@ -172,6 +172,7 @@ constexpr inline GasCostTable gas_costs = []() noexcept {
     table[EVMC_CANCUN][OP_CALLF] = 5;
     table[EVMC_CANCUN][OP_RETF] = 3;
     table[EVMC_CANCUN][OP_DATALOAD] = 3;
+    table[EVMC_CANCUN][OP_DATASIZE] = 2;
 
     table[EVMC_PRAGUE] = table[EVMC_CANCUN];
 
@@ -377,6 +378,7 @@ constexpr inline std::array<Traits, 256> traits = []() noexcept {
     table[OP_DUPN] = {"DUPN", 1, false, 0, 1, EVMC_CANCUN};
     table[OP_SWAPN] = {"SWAPN", 1, false, 0, 0, EVMC_CANCUN};
     table[OP_DATALOAD] = {"DATALOAD", 0, false, 1, 0, EVMC_CANCUN};
+    table[OP_DATASIZE] = {"DATASIZE", 0, false, 0, 1, EVMC_CANCUN};
 
     table[OP_CREATE] = {"CREATE", 0, false, 3, -2, EVMC_FRONTIER};
     table[OP_CALL] = {"CALL", 0, false, 7, -6, EVMC_FRONTIER};
diff --git a/lib/evmone/instructions_xmacro.hpp b/lib/evmone/instructions_xmacro.hpp
index 342aae0d12..b8c9caaff1 100644
--- a/lib/evmone/instructions_xmacro.hpp
+++ b/lib/evmone/instructions_xmacro.hpp
@@ -227,7 +227,7 @@
     ON_OPCODE_IDENTIFIER(OP_DUPN, dupn)                     \
     ON_OPCODE_IDENTIFIER(OP_SWAPN, swapn)                   \
     ON_OPCODE_IDENTIFIER(OP_DATALOAD, dataload)             \
-    ON_OPCODE_UNDEFINED(0xb8)                               \
+    ON_OPCODE_IDENTIFIER(OP_DATASIZE, datasize)             \
     ON_OPCODE_UNDEFINED(0xb9)                               \
     ON_OPCODE_UNDEFINED(0xba)                               \
     ON_OPCODE_UNDEFINED(0xbb)                               \
diff --git a/test/unittests/instructions_test.cpp b/test/unittests/instructions_test.cpp
index 84c6062743..5469722035 100644
--- a/test/unittests/instructions_test.cpp
+++ b/test/unittests/instructions_test.cpp
@@ -111,6 +111,7 @@ constexpr bool instruction_only_in_evmone(evmc_revision rev, Opcode op) noexcept
     case OP_DUPN:
     case OP_SWAPN:
     case OP_DATALOAD:
+    case OP_DATASIZE:
         return true;
     default:
         return false;