diff --git a/core/relinker/codegen/include/codegen/x86/X64OpcodeConstants.hpp b/core/relinker/codegen/include/codegen/x86/X64OpcodeConstants.hpp
index 889d0c447..7a9a14a36 100644
--- a/core/relinker/codegen/include/codegen/x86/X64OpcodeConstants.hpp
+++ b/core/relinker/codegen/include/codegen/x86/X64OpcodeConstants.hpp
@@ -170,6 +170,7 @@ inline constexpr std::uint8_t TwoByteGrp6 = 0x00;
 inline constexpr std::uint8_t TwoByteLar = 0x02;
 inline constexpr std::uint8_t TwoByteLsl = 0x03;
 inline constexpr std::uint8_t TwoBytePrefetchw = 0x0D;
+inline constexpr std::uint8_t TwoByte3DNow = 0x0F;
 inline constexpr std::uint8_t TwoByteMovCrDrMin = 0x20;
 inline constexpr std::uint8_t TwoByteMovCrDrMax = 0x23;
 inline constexpr std::uint8_t TwoBytePopcnt = 0xB8;
diff --git a/core/relinker/codegen/src/x86/X64InstructionDecoder.cpp b/core/relinker/codegen/src/x86/X64InstructionDecoder.cpp
index b894332bd..4f9ff5b3b 100644
--- a/core/relinker/codegen/src/x86/X64InstructionDecoder.cpp
+++ b/core/relinker/codegen/src/x86/X64InstructionDecoder.cpp
@@ -242,7 +242,7 @@ std::size_t X64InstructionDecoder::Decode(const std::uint8_t* data, std::size_t
             hasModRm = true;
         } else if (opcode >= TwoByteJccRel32Min && opcode <= TwoByteJccRel32Max) {
             immediateSize = ImmSize32;
-        } else if (opcode == TwoByteMovImm8ModRm) {
+        } else if (opcode == TwoByteMovImm8ModRm || opcode == TwoByte3DNow) {
             hasModRm = true;
             immediateSize = ImmSize8;
         } else if (opcode >= TwoByteShiftImm8Min && opcode <= TwoByteShiftImm8Max) {
@@ -556,7 +556,7 @@ DecodedInstructionInfo X64InstructionDecoder::DecodeInstruction(
             op == TwoByteImulRmModRm || op == TwoByteGrp7 ||
             op == TwoByteGrp15 || op == TwoByteXadd ||
             op == TwoByteGrp9 || op == TwoByteNopModRm ||
-            op == TwoByteEndbr || op == TwoByteMovImm8ModRm ||
+            op == TwoByteEndbr || op == TwoByteMovImm8ModRm || op == TwoByte3DNow ||
             op == ThreeByteEscape38 || op == ThreeByteEscape3A ||
             (op >= TwoByteShiftImm8Min && op <= TwoByteShiftImm8Max) ||
             op == TwoByteShldImm8 || op == TwoByteShrdImm8 ||
diff --git a/core/relinker/codegen/tests/DecoderLengthCases.hpp b/core/relinker/codegen/tests/DecoderLengthCases.hpp
index 561f3a64e..10747c9a6 100644
--- a/core/relinker/codegen/tests/DecoderLengthCases.hpp
+++ b/core/relinker/codegen/tests/DecoderLengthCases.hpp
@@ -33,6 +33,12 @@ inline constexpr DecoderLengthCase kDecoderLengthCases[] = {
     {"0f0b", 2},
     {"0f0d846511223344", 8},
     {"0f0e", 2},
+    {"0f0fc196", 4},
+    {"0f0f08b7", 4},
+    {"0f0f4f80b4", 5},
+    {"0f0f846511223344b4", 9},
+    {"0f0f0d11223344a6", 8},
+    {"410f0f1c24bf", 6},
     {"0f10846511223344", 8},
     {"0f11846511223344", 8},
     {"0f12846511223344", 8},
diff --git a/core/relinker/codegen/tests/DecoderLengthTests.cpp b/core/relinker/codegen/tests/DecoderLengthTests.cpp
index d119b3b32..e141e1539 100644
--- a/core/relinker/codegen/tests/DecoderLengthTests.cpp
+++ b/core/relinker/codegen/tests/DecoderLengthTests.cpp
@@ -77,6 +77,10 @@ int main() {
             } catch (const Codegen::CodegenException&) {
             }
         }
+        const auto threeDNow = parse("0f0f0d11223344a6");
+        const auto threeDNowInfo = decoder.DecodeInstruction(threeDNow.data(), threeDNow.size());
+        require(threeDNowInfo.HasModRm && threeDNowInfo.ModRmByte == 0x0d, "3DNow! ModRM was not reported");
+        require(threeDNowInfo.HasRipRelativeDisp && threeDNowInfo.RipRelativeDispOffset == 3, "3DNow! RIP-relative displacement was not reported");
         std::cout << "Decoder length tests passed\n";
     } catch (const std::exception& error) {
         std::cerr << error.what() << '\n';