diff --git a/src/runtime/sys_darwin_arm64.s b/src/runtime/sys_darwin_arm64.s
index 788fdf87b77..a3901bdb3bf 100644
--- a/src/runtime/sys_darwin_arm64.s
+++ b/src/runtime/sys_darwin_arm64.s
@@ -724,13 +724,9 @@ TEXT runtime·syscall9(SB),NOSPLIT,$0
 	MOVD	56(R0), R6	// a7
 	MOVD	64(R0), R7	// a8
 	MOVD	72(R0), R8	// a9
+	MOVD	R8, 0(RSP)	// the 9th arg and onwards must be passed on the stack
 	MOVD	8(R0), R0	// a1
 
-	// If fn is declared as vararg, we have to pass the vararg arguments on the stack.
-	// See syscall above. The only function this applies to is openat, for which the 4th
-	// arg must be on the stack.
-	MOVD	R3, (RSP)
-
 	BL	(R12)
 
 	MOVD	8(RSP), R2	// pop structure pointer
diff --git a/src/runtime/syscall_test.go b/src/runtime/syscall_test.go
new file mode 100644
index 00000000000..18f3e8e3151
--- /dev/null
+++ b/src/runtime/syscall_test.go
@@ -0,0 +1,28 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime_test
+
+import (
+	"internal/testenv"
+	"runtime"
+	"testing"
+)
+
+func TestSyscallArgs(t *testing.T) {
+	if runtime.GOOS != "darwin" {
+		t.Skipf("skipping test: GOARCH=%s", runtime.GOARCH)
+	}
+	testenv.MustHaveCGO(t)
+
+	exe, err := buildTestProg(t, "testsyscall")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cmd := testenv.Command(t, exe)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		t.Fatalf("test program failed: %v\n%s", err, out)
+	}
+}
diff --git a/src/runtime/testdata/testsyscall/testsyscall.go b/src/runtime/testdata/testsyscall/testsyscall.go
new file mode 100644
index 00000000000..23cca16494d
--- /dev/null
+++ b/src/runtime/testdata/testsyscall/testsyscall.go
@@ -0,0 +1,65 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	_ "runtime/testdata/testsyscall/testsyscallc" // unfortunately, we can't put C and assembly in the package
+	_ "unsafe"                                    // for go:linkname
+)
+
+//go:linkname syscall_syscall syscall.syscall
+func syscall_syscall(fn, a1, a2, a3 uintptr) (r1, r2, err uintptr)
+
+//go:linkname syscall_syscall6 syscall.syscall6
+func syscall_syscall6(fn, a1, a2, a3, a4, a5, a6 uintptr) (r1, r2, err uintptr)
+
+//go:linkname syscall_syscall9 syscall.syscall9
+func syscall_syscall9(fn, a1, a2, a3, a4, a5, a6, a7, a8, a9 uintptr) (r1, r2, err uintptr)
+
+var (
+	syscall_check0_trampoline_addr uintptr
+	syscall_check1_trampoline_addr uintptr
+	syscall_check2_trampoline_addr uintptr
+	syscall_check3_trampoline_addr uintptr
+	syscall_check4_trampoline_addr uintptr
+	syscall_check5_trampoline_addr uintptr
+	syscall_check6_trampoline_addr uintptr
+	syscall_check7_trampoline_addr uintptr
+	syscall_check8_trampoline_addr uintptr
+	syscall_check9_trampoline_addr uintptr
+)
+
+func main() {
+	if ret, _, _ := syscall_syscall(syscall_check0_trampoline_addr, 0, 0, 0); ret != 1 {
+		panic("hello0")
+	}
+	if ret, _, _ := syscall_syscall(syscall_check1_trampoline_addr, 1, 0, 0); ret != 1 {
+		panic("hello1")
+	}
+	if ret, _, _ := syscall_syscall(syscall_check2_trampoline_addr, 1, 2, 0); ret != 1 {
+		panic("hello2")
+	}
+	if ret, _, _ := syscall_syscall(syscall_check3_trampoline_addr, 1, 2, 3); ret != 1 {
+		panic("hello3")
+	}
+	if ret, _, _ := syscall_syscall6(syscall_check4_trampoline_addr, 1, 2, 3, 4, 0, 0); ret != 1 {
+		panic("hello4")
+	}
+	if ret, _, _ := syscall_syscall6(syscall_check5_trampoline_addr, 1, 2, 3, 4, 5, 0); ret != 1 {
+		panic("hello5")
+	}
+	if ret, _, _ := syscall_syscall6(syscall_check6_trampoline_addr, 1, 2, 3, 4, 5, 6); ret != 1 {
+		panic("hello6")
+	}
+	if ret, _, _ := syscall_syscall9(syscall_check7_trampoline_addr, 1, 2, 3, 4, 5, 6, 7, 0, 0); ret != 1 {
+		panic("hello7")
+	}
+	if ret, _, _ := syscall_syscall9(syscall_check8_trampoline_addr, 1, 2, 3, 4, 5, 6, 7, 8, 0); ret != 1 {
+		panic("hello8")
+	}
+	if ret, _, _ := syscall_syscall9(syscall_check9_trampoline_addr, 1, 2, 3, 4, 5, 6, 7, 8, 9); ret != 1 {
+		panic("hello9")
+	}
+}
diff --git a/src/runtime/testdata/testsyscall/testsyscall.s b/src/runtime/testdata/testsyscall/testsyscall.s
new file mode 100644
index 00000000000..c8d556dfd9a
--- /dev/null
+++ b/src/runtime/testdata/testsyscall/testsyscall.s
@@ -0,0 +1,55 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#include "textflag.h"
+
+TEXT syscall_check0_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check0(SB)
+GLOBL   ·syscall_check0_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check0_trampoline_addr(SB)/8, $syscall_check0_trampoline<>(SB)
+
+TEXT syscall_check1_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check1(SB)
+GLOBL   ·syscall_check1_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check1_trampoline_addr(SB)/8, $syscall_check1_trampoline<>(SB)
+
+TEXT syscall_check2_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check2(SB)
+GLOBL   ·syscall_check2_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check2_trampoline_addr(SB)/8, $syscall_check2_trampoline<>(SB)
+
+TEXT syscall_check3_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check3(SB)
+GLOBL   ·syscall_check3_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check3_trampoline_addr(SB)/8, $syscall_check3_trampoline<>(SB)
+
+TEXT syscall_check4_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check4(SB)
+GLOBL   ·syscall_check4_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check4_trampoline_addr(SB)/8, $syscall_check4_trampoline<>(SB)
+
+TEXT syscall_check5_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check5(SB)
+GLOBL   ·syscall_check5_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check5_trampoline_addr(SB)/8, $syscall_check5_trampoline<>(SB)
+
+TEXT syscall_check6_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check6(SB)
+GLOBL   ·syscall_check6_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check6_trampoline_addr(SB)/8, $syscall_check6_trampoline<>(SB)
+
+TEXT syscall_check7_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check7(SB)
+GLOBL   ·syscall_check7_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check7_trampoline_addr(SB)/8, $syscall_check7_trampoline<>(SB)
+
+TEXT syscall_check8_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check8(SB)
+GLOBL   ·syscall_check8_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check8_trampoline_addr(SB)/8, $syscall_check8_trampoline<>(SB)
+
+TEXT syscall_check9_trampoline<>(SB),NOSPLIT,$0-0
+    JMP syscall_check9(SB)
+GLOBL   ·syscall_check9_trampoline_addr(SB), RODATA, $8
+DATA    ·syscall_check9_trampoline_addr(SB)/8, $syscall_check9_trampoline<>(SB)
diff --git a/src/runtime/testdata/testsyscall/testsyscallc/testsyscallc.go b/src/runtime/testdata/testsyscall/testsyscallc/testsyscallc.go
new file mode 100644
index 00000000000..0b2a220b590
--- /dev/null
+++ b/src/runtime/testdata/testsyscall/testsyscallc/testsyscallc.go
@@ -0,0 +1,48 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package testsyscallc
+
+/*
+int syscall_check0(void) {
+    return 1;
+}
+
+int syscall_check1(int a1) {
+    return a1 == 1;
+}
+
+int syscall_check2(int a1, int a2) {
+    return a1 == 1 && a2 == 2;
+}
+
+int syscall_check3(int a1, int a2, int a3) {
+    return a1 == 1 && a2 == 2 && a3 == 3;
+}
+
+int syscall_check4(int a1, int a2, int a3, int a4) {
+    return a1 == 1 && a2 == 2 && a3 == 3 && a4 == 4;
+}
+
+int syscall_check5(int a1, int a2, int a3, int a4, int a5) {
+    return a1 == 1 && a2 == 2 && a3 == 3 && a4 == 4 && a5 == 5;
+}
+
+int syscall_check6(int a1, int a2, int a3, int a4, int a5, int a6) {
+    return a1 == 1 && a2 == 2 && a3 == 3 && a4 == 4 && a5 == 5 && a6 == 6;
+}
+
+int syscall_check7(int a1, int a2, int a3, int a4, int a5, int a6, int a7) {
+    return a1 == 1 && a2 == 2 && a3 == 3 && a4 == 4 && a5 == 5 && a6 == 6 && a7 == 7;
+}
+
+int syscall_check8(int a1, int a2, int a3, int a4, int a5, int a6, int a7, int a8) {
+    return a1 == 1 && a2 == 2 && a3 == 3 && a4 == 4 && a5 == 5 && a6 == 6 && a7 == 7 && a8 == 8;
+}
+
+int syscall_check9(int a1, int a2, int a3, int a4, int a5, int a6, int a7, int a8, int a9) {
+    return a1 == 1 && a2 == 2 && a3 == 3 && a4 == 4 && a5 == 5 && a6 == 6 && a7 == 7 && a8 == 8 && a9 == 9;
+}
+*/
+import "C"