diff --git a/unix/linux/mksysnum.go b/unix/linux/mksysnum.go
index 60d7e235..2b5a6bf7 100644
--- a/unix/linux/mksysnum.go
+++ b/unix/linux/mksysnum.go
@@ -8,11 +8,11 @@ package main
 
 import (
 	"bufio"
+	"bytes"
 	"fmt"
 	"os"
 	"os/exec"
 	"regexp"
-	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -127,16 +127,17 @@ func main() {
 		os.Exit(1)
 	}
 
-	if slices.Contains([]string{"riscv64", "loong64", "arm64"}, goarch) {
-		// Kernel linux v6.11 removed some __NR_* constants that only
+	switch goarch {
+	case "riscv64", "loong64", "arm64":
+		// Kernel linux v6.11 removed some __NR_* macros that only
 		// existed on some architectures as an implementation detail. In
 		// order to keep backwards compatibility we add them back.
 		//
-		// See https://lkml.org/lkml/2024/8/5/1283
-		if !strings.Contains(string(cmd), "#define __NR_arch_specific_syscall") {
+		// See https://lkml.org/lkml/2024/8/5/1283.
+		if !bytes.Contains(cmd, []byte("#define __NR_arch_specific_syscall")) {
 			cmd = append(cmd, []byte("#define __NR_arch_specific_syscall 244\n")...)
 		}
-		if !strings.Contains(string(cmd), "#define __NR_fstatat") {
+		if !bytes.Contains(cmd, []byte("#define __NR_fstatat")) {
 			cmd = append(cmd, []byte("#define __NR_fstatat 79\n")...)
 		}
 	}