diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -343,6 +343,14 @@
 	 * the postsig() loop was performed.
 	 */
 	sigfastblock_setpend(td, resched_sigs);
+
+	/*
+	 * Clear td_sa.code: signal to ptrace that syscall arguments
+	 * are unavailable after this point. This AST handler is the
+	 * last chance for ptracestop() to signal the tracer before
+	 * the tracee returns to userspace.
+	 */
+	td->td_sa.code = 0;
 }
 
 static void
diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -1168,7 +1168,8 @@
 
 	case PT_GET_SC_ARGS:
 		CTR1(KTR_PTRACE, "PT_GET_SC_ARGS: pid %d", p->p_pid);
-		if ((td2->td_dbgflags & (TDB_SCE | TDB_SCX)) == 0
+		if (((td2->td_dbgflags & (TDB_SCE | TDB_SCX)) == 0 &&
+		     td2->td_sa.code == 0)
 #ifdef COMPAT_FREEBSD32
 		    || (wrap32 && !safe)
 #endif
@@ -1511,12 +1512,9 @@
 		pl->pl_sigmask = td2->td_sigmask;
 		pl->pl_siglist = td2->td_siglist;
 		strcpy(pl->pl_tdname, td2->td_name);
-		if ((td2->td_dbgflags & (TDB_SCE | TDB_SCX)) != 0) {
+		if (td2->td_sa.code != 0) {
 			pl->pl_syscall_code = td2->td_sa.code;
 			pl->pl_syscall_narg = td2->td_sa.callp->sy_narg;
-		} else {
-			pl->pl_syscall_code = 0;
-			pl->pl_syscall_narg = 0;
 		}
 		CTR6(KTR_PTRACE,
     "PT_LWPINFO: tid %d (pid %d) event %d flags %#x child pid %d syscall %d",