diff --git a/ape/ape-m1.c b/ape/ape-m1.c
index 874f452e1..4c32ebf85 100644
--- a/ape/ape-m1.c
+++ b/ape/ape-m1.c
@@ -726,10 +726,10 @@ __attribute__((__noreturn__)) static void Spawn(const char *exe, int fd,
 
   register long *x0 __asm__("x0") = sp;
   register char *x2 __asm__("x2") = path;
+  register int   x3 __asm__("x3") = 8;  /* _HOSTXNU */
   register struct Syslib *x15 __asm__("x15") = lib;
   register long x16 __asm__("x16") = e->e_entry;
   __asm__ volatile("mov\tx1,#0\n\t"
-                   "mov\tx3,#0\n\t"
                    "mov\tx4,#0\n\t"
                    "mov\tx5,#0\n\t"
                    "mov\tx6,#0\n\t"
@@ -758,7 +758,7 @@ __attribute__((__noreturn__)) static void Spawn(const char *exe, int fd,
                    "mov\tx0,#0\n\t"
                    "br\tx16"
                    : /* no outputs */
-                   : "r"(x0), "r"(x2), "r"(x15), "r"(x16)
+                   : "r"(x0), "r"(x2), "r"(x3), "r"(x15), "r"(x16)
                    : "memory");
   __builtin_unreachable();
 }
diff --git a/ape/launch.S b/ape/launch.S
index 87489f9f5..ae2cb58a1 100644
--- a/ape/launch.S
+++ b/ape/launch.S
@@ -32,15 +32,15 @@
 //	@param	rdi is passed through as-is
 //	@param	rsi is address of entrypoint (becomes zero)
 //	@param	rdx is passed through as-is
-//	@param	rcx is stack pointer (becomes r8)
+//	@param	rcx is passed through as-is
+//	@param	r8  is stack pointer (becomes zero)
 //	@noreturn
 Launch:
 #ifdef __aarch64__
 
 	mov	x16,x1
-	mov	sp,x3
+	mov	sp,x4
 	mov	x1,0
-	mov	x3,x4
 	mov	x4,0
 	mov	x5,0
 	mov	x6,0
@@ -70,8 +70,7 @@ Launch:
 
 #else
 
-	mov	%rcx,%rsp
-	mov	%r8,%rcx
+	mov	%r8,%rsp
 	xor	%r8d,%r8d
 	xor	%r9d,%r9d
 	xor	%r10d,%r10d
diff --git a/ape/loader.c b/ape/loader.c
index ece126229..ce9ef1b9c 100644
--- a/ape/loader.c
+++ b/ape/loader.c
@@ -225,7 +225,7 @@ struct ApeLoader {
 
 EXTERN_C long SystemCall(long, long, long, long, long, long, long, int);
 EXTERN_C void
-Launch(void *, long, void *, void *, int) __attribute__((__noreturn__));
+Launch(void *, long, void *, int, void *) __attribute__((__noreturn__));
 
 extern char __executable_start[];
 extern char _end[];
@@ -768,7 +768,7 @@ __attribute__((__noreturn__)) static void Spawn(int os, char *exe, int fd,
   Msyscall(dynbase + code, codesize, os);
 
   /* call program entrypoint */
-  Launch(IsFreebsd() ? sp : 0, dynbase + e->e_entry, exe, sp, os);
+  Launch(IsFreebsd() ? sp : 0, dynbase + e->e_entry, exe, os, sp);
 }
 
 static const char *TryElf(struct ApeLoader *M, union ElfEhdrBuf *ebuf,
diff --git a/libc/crt/crt.S b/libc/crt/crt.S
index 07978f47b..2f9fbb28c 100644
--- a/libc/crt/crt.S
+++ b/libc/crt/crt.S
@@ -143,6 +143,7 @@ _start:
 	mov	x1,x15
 
 //	third arg (x2) is the program path passed by ape-m1.c
+//	fourth arg (x3) is os
 
 //	switch to c code
 	bl	cosmo