diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 5293d53c164..38bce7a8952 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -633,6 +633,13 @@ sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask)
 	sf.sf_uc.uc_mcontext.mc_gs = rgs();
 	bcopy(regs, &sf.sf_uc.uc_mcontext.mc_fs, sizeof(*regs));
 	sf.sf_uc.uc_mcontext.mc_len = sizeof(sf.sf_uc.uc_mcontext); /* magic */
+
+	/*
+	 * The get_fpcontext() call must be placed before assignments
+	 * to mc_fsbase and mc_gsbase due to the alignment-override
+	 * code in get_fpcontext() that possibly clobbers 12 bytes of
+	 * mcontext after mc_fpstate.
+	 */
 	get_fpcontext(td, &sf.sf_uc.uc_mcontext);
 	fpstate_drop(td);
 	/*
@@ -3240,6 +3247,13 @@ get_mcontext(struct thread *td, mcontext_t *mcp, int flags)
 	mcp->mc_esp = tp->tf_esp;
 	mcp->mc_ss = tp->tf_ss;
 	mcp->mc_len = sizeof(*mcp);
+
+	/*
+	 * The get_fpcontext() call must be placed before assignments
+	 * to mc_fsbase and mc_gsbase due to the alignment-override
+	 * code in get_fpcontext() that possibly clobbers 12 bytes of
+	 * mcontext after mc_fpstate.
+	 */
 	get_fpcontext(td, mcp);
 	sdp = &td->td_pcb->pcb_gsd;
 	mcp->mc_fsbase = sdp->sd_hibase << 24 | sdp->sd_lobase;