diff --git a/arch/x86_64/kernel/include/signal.h b/arch/x86_64/kernel/include/signal.h
index 9e3989cd..18d587f6 100644
--- a/arch/x86_64/kernel/include/signal.h
+++ b/arch/x86_64/kernel/include/signal.h
@@ -18,6 +18,11 @@
 #define _NSIG_BPW	64
 #define _NSIG_WORDS (_NSIG / _NSIG_BPW)
 
+static inline int valid_signal(unsigned long sig)
+{
+	return sig <= _NSIG ? 1 : 0;
+}
+
 typedef unsigned long int __sigset_t;
 #define __sigmask(sig)  (((__sigset_t) 1) << ((sig) - 1))
 
diff --git a/arch/x86_64/kernel/syscall.c b/arch/x86_64/kernel/syscall.c
index 5e20d480..a2605089 100644
--- a/arch/x86_64/kernel/syscall.c
+++ b/arch/x86_64/kernel/syscall.c
@@ -143,8 +143,6 @@ SYSCALL_DECLARE(rt_sigaction)
 	struct k_sigaction new_sa, old_sa;
 	int rc;
 
-	if(sig == SIGKILL || sig == SIGSTOP || sig <= 0 || sig > 64)
-		return -EINVAL;
 	if (sigsetsize != sizeof(sigset_t))
 		return -EINVAL;
 
diff --git a/kernel/syscall.c b/kernel/syscall.c
index fee627f1..08b97751 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -3059,6 +3059,13 @@ do_sigaction(int sig, struct k_sigaction *act, struct k_sigaction *oact)
 	struct mcs_rwlock_node_irqsave mcs_rw_node;
 	ihk_mc_user_context_t ctx0;
 
+	if (!valid_signal(sig) || sig < 1) {
+		return -EINVAL;
+	}
+	if (act && (sig == SIGKILL || sig == SIGSTOP)) {
+		return -EINVAL;
+	}
+
 	mcs_rwlock_writer_lock(&thread->sigcommon->lock, &mcs_rw_node);
 	k = thread->sigcommon->action + sig - 1;
 	if(oact)