diff --git a/ChangeLog b/ChangeLog
index acf8de672e..6d7bbe78a6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jul 26 11:29:01 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* signal.c (default_handler, Init_signal): discard SIGSYS, ENOSYS
+	  should raise a SystemCallError always instead.
+
 Sun Jul 26 10:26:35 2015  Aaron Patterson <tenderlove@ruby-lang.org>
 
 	* ext/openssl/ossl_ssl.c (ossl_call_servername_cb): set the ssl context
diff --git a/signal.c b/signal.c
index 5d5cb6b2b6..34d229a71d 100644
--- a/signal.c
+++ b/signal.c
@@ -935,6 +935,13 @@ check_reserved_signal_(const char *name, size_t name_len)
 }
 #endif
 
+#ifdef SIGSYS
+static RETSIGTYPE
+sig_do_nothing(int sig)
+{
+}
+#endif
+
 static void
 signal_exec(VALUE cmd, int safe, int sig)
 {
@@ -1061,6 +1068,11 @@ default_handler(int sig)
       case SIGPIPE:
         func = SIG_IGN;
         break;
+#endif
+#ifdef SIGSYS
+      case SIGSYS:
+        func = sig_do_nothing;
+        break;
 #endif
       default:
         func = SIG_DFL;
@@ -1477,6 +1489,9 @@ Init_signal(void)
 #ifdef SIGPIPE
     install_sighandler(SIGPIPE, SIG_IGN);
 #endif
+#ifdef SIGSYS
+    install_sighandler(SIGSYS, sig_do_nothing);
+#endif
 
 #if defined(SIGCLD)
     init_sigchld(SIGCLD);