diff --git a/src/os/mac/macho/MachO.go b/src/os/mac/macho/MachO.go
index 449c11b..d48281c 100644
--- a/src/os/mac/macho/MachO.go
+++ b/src/os/mac/macho/MachO.go
@@ -24,8 +24,8 @@ func New(code []byte, data []byte) *MachO {
 			Architecture:      CPU_X86_64,
 			MicroArchitecture: 3 | 0x80000000,
 			Type:              TypeExecute,
-			NumCommands:       4,
-			SizeCommands:      72*3 + 184,
+			NumCommands:       5,
+			SizeCommands:      72*4 + 184,
 			Flags:             FlagNoUndefs,
 			Reserved:          0,
 		},
@@ -53,19 +53,32 @@ func (m *MachO) Write(writer io.Writer) {
 	})
 
 	codePadding := common.Padding(32+m.Header.SizeCommands, config.Align)
-	codeLength := uint64(len(m.Code))
-	codeEnd := config.CodeOffset + codeLength
+	codeEnd := uint64(config.CodeOffset + len(m.Code))
 	dataPadding := common.Padding(codeEnd, config.Align)
 	dataStart := codeEnd + dataPadding
 
+	binary.Write(writer, binary.LittleEndian, &Segment64{
+		LoadCommand:  LcSegment64,
+		Length:       72,
+		Name:         [16]byte{'_', '_', 'H', 'E', 'A', 'D'},
+		Address:      config.BaseAddress,
+		SizeInMemory: config.CodeOffset,
+		Offset:       0,
+		SizeInFile:   config.CodeOffset,
+		NumSections:  0,
+		Flag:         0,
+		MaxProt:      ProtReadable | ProtExecutable,
+		InitProt:     ProtReadable | ProtExecutable,
+	})
+
 	binary.Write(writer, binary.LittleEndian, &Segment64{
 		LoadCommand:  LcSegment64,
 		Length:       72,
 		Name:         [16]byte{'_', '_', 'T', 'E', 'X', 'T'},
 		Address:      config.BaseAddress + config.CodeOffset,
-		SizeInMemory: codeLength,
+		SizeInMemory: uint64(len(m.Code)),
 		Offset:       config.CodeOffset,
-		SizeInFile:   codeLength,
+		SizeInFile:   uint64(len(m.Code)),
 		NumSections:  0,
 		Flag:         0,
 		MaxProt:      ProtReadable | ProtExecutable,