diff --git a/lib/libc/i386/gen/signalcontext.c b/lib/libc/i386/gen/signalcontext.c
index a66e2db16fc3..50c4889a0df5 100644
--- a/lib/libc/i386/gen/signalcontext.c
+++ b/lib/libc/i386/gen/signalcontext.c
@@ -56,7 +56,8 @@ __signalcontext(ucontext_t *ucp, int sig, __sighandler_t *func)
 	 */
 	p = (register_t *)(void *)(intptr_t)ucp->uc_mcontext.mc_esp;
 	*--p = (register_t)(intptr_t)ucp;
-	p -= sizeof(struct sigframe);
+	p = (register_t *)((u_register_t)p & ~0xF);  /* Align to 16 bytes. */
+	p = (register_t *)((u_register_t)p - sizeof(struct sigframe));
 	sfp = (struct sigframe *)p;
 	bzero(sfp, sizeof(struct sigframe));
 	sfp->sf_signum = sig;