diff --git a/lib/libc/aarch64/gen/setjmp.S b/lib/libc/aarch64/gen/setjmp.S
--- a/lib/libc/aarch64/gen/setjmp.S
+++ b/lib/libc/aarch64/gen/setjmp.S
@@ -73,13 +73,19 @@
 END(setjmp)
 
 ENTRY(longjmp)
+	/* Check the magic value */
+	ldr	x8, [x0], #8
+	ldr	x9, .Lmagic
+	cmp	x8, x9
+	b.ne	botch
+
 	sub	sp, sp, #32
 	stp	x0, lr, [sp]
 	str	x1, [sp, #16]
 
 	/* Restore the signal mask */
 	mov	x2, #0				/* oset */
-	add	x1, x0, #(_JB_SIGMASK * 8)	/* set */
+	add	x1, x0, #(_JB_SIGMASK * 8 - 8)	/* set */
 	mov	x0, #3				/* SIG_SETMASK */
 	bl	sigprocmask
 
@@ -87,12 +93,6 @@
 	ldp	x0, lr, [sp]
 	add	sp, sp, #32
 
-	/* Check the magic value */
-	ldr	x8, [x0], #8
-	ldr	x9, .Lmagic
-	cmp	x8, x9
-	b.ne	botch
-
 	/* Restore the stack pointer */
 	ldr	x8, [x0], #8
 	mov	sp, x8