diff --git a/tests/sys/kern/Makefile b/tests/sys/kern/Makefile
--- a/tests/sys/kern/Makefile
+++ b/tests/sys/kern/Makefile
@@ -49,6 +49,7 @@
 ATF_TESTS_C+=	waitpid_nohang
 ATF_TESTS_C+=	pdeathsig
 ATF_TESTS_C+=	sigsys
+TEST_METADATA.sigsys+=	is_exclusive="true"
 
 ATF_TESTS_SH+=	coredump_phnum_test
 ATF_TESTS_SH+=	sonewconn_overflow
diff --git a/tests/sys/kern/sigsys.c b/tests/sys/kern/sigsys.c
--- a/tests/sys/kern/sigsys.c
+++ b/tests/sys/kern/sigsys.c
@@ -7,31 +7,29 @@
  * under sponsorship from the FreeBSD Foundation.
  */
 
+#include <sys/param.h>
 #include <sys/syscall.h>
+#include <sys/sysctl.h>
 
 #include <atf-c.h>
 #include <errno.h>
 #include <signal.h>
 #include <stdatomic.h>
 #include <stdbool.h>
+#include <stdio.h>
 
 static sig_atomic_t sigsys_cnt;
 
+#define	SAVEDVALUE	"savedsignosys"
+
 static void
 sigsys_handler(int signo, siginfo_t *si, void *ucp)
 {
 	sigsys_cnt++;
 }
 
-ATF_TC(sigsys_test);
-
-ATF_TC_HEAD(sigsys_test, tc)
-{
-	atf_tc_set_md_var(tc, "descr",
-	    "Testing delivery of SIGSYS on invalid syscalls");
-}
-
-ATF_TC_BODY(sigsys_test, tc)
+static void
+sigsys_test(int knob)
 {
 	struct sigaction sa;
 
@@ -43,27 +41,102 @@
 	ATF_REQUIRE(syscall(273) == -1);	/* reserved */
 	ATF_CHECK_ERRNO(ENOSYS, true);
 	atomic_signal_fence(memory_order_seq_cst);
-	ATF_CHECK_EQ(1, sigsys_cnt);
+	ATF_CHECK_EQ(1 * knob, sigsys_cnt * knob);
 
 	ATF_REQUIRE(syscall(440) == -1);	/* SYS_kse_switchin */
 	ATF_CHECK_ERRNO(ENOSYS, true);
 	atomic_signal_fence(memory_order_seq_cst);
-	ATF_CHECK_EQ(2, sigsys_cnt);
+	ATF_CHECK_EQ(2 * knob, sigsys_cnt * knob);
 
 	/* Hope this is enough for say next two months */
 	ATF_REQUIRE(syscall(3000000) == -1);
 	ATF_CHECK_ERRNO(ENOSYS, true);
 	atomic_signal_fence(memory_order_seq_cst);
-	ATF_CHECK_EQ(3, sigsys_cnt);
+	ATF_CHECK_EQ(3 * knob, sigsys_cnt * knob);
 
 	ATF_REQUIRE(syscall(SYS_afs3_syscall) == -1);
 	ATF_CHECK_ERRNO(ENOSYS, true);
 	atomic_signal_fence(memory_order_seq_cst);
-	ATF_CHECK_EQ(4, sigsys_cnt);
+	ATF_CHECK_EQ(4 * knob, sigsys_cnt * knob);
+}
+
+static void
+sysctlset(const char *name, int val)
+{
+	size_t oldlen;
+	int oldval;
+	char buf[80];
+
+	ATF_REQUIRE(sysctlbyname(name, &oldval, &oldlen, NULL, 0) == 0);
+
+	/* Store old %name in a symlink for cleanup */
+	snprintf(buf, sizeof(buf), "%d", oldval);
+	ATF_REQUIRE(symlink(buf, SAVEDVALUE) == 0);
+
+	ATF_REQUIRE(sysctlbyname(name, NULL, NULL, &val, sizeof(val)) == 0);
+}
+
+static void
+sysctlcleanup(const char *name)
+{
+	size_t oldlen;
+	int n, oldval;
+	char buf[80];
+
+	if ((n = readlink(SAVEDVALUE, buf, sizeof(buf))) > 0) {
+		buf[MIN((size_t)n, sizeof(buf) - 1)] = '\0';
+		if (sscanf(buf, "%d", &oldval) == 1) {
+			oldlen = sizeof(oldval);
+			(void)sysctlbyname(name, NULL, 0,
+			    &oldval, oldlen);
+		}
+	}
+	(void)unlink(SAVEDVALUE);
+}
+
+ATF_TC_WITH_CLEANUP(sigsys_test_on);
+ATF_TC_HEAD(sigsys_test_on, tc)
+{
+	atf_tc_set_md_var(tc, "require.user", "root");
+	atf_tc_set_md_var(tc, "require.config", "allow_sysctl_side_effects");
+	atf_tc_set_md_var(tc, "descr",
+	    "Testing delivery of SIGSYS on invalid syscalls");
+}
+
+ATF_TC_BODY(sigsys_test_on, tc)
+{
+	sysctlset("kern.signosys", 1);
+	sigsys_test(1);
+}
+
+ATF_TC_CLEANUP(sigsys_test_on, tc)
+{
+	sysctlcleanup("kern.signosys");
+}
+
+ATF_TC_WITH_CLEANUP(sigsys_test_off);
+ATF_TC_HEAD(sigsys_test_off, tc)
+{
+	atf_tc_set_md_var(tc, "require.user", "root");
+	atf_tc_set_md_var(tc, "require.config", "allow_sysctl_side_effects");
+	atf_tc_set_md_var(tc, "descr",
+	    "Testing SIGSYS silence on invalid syscalls");
+}
+
+ATF_TC_BODY(sigsys_test_off, tc)
+{
+	sysctlset("kern.signosys", 0);
+	sigsys_test(0);
+}
+
+ATF_TC_CLEANUP(sigsys_test_off, tc)
+{
+	sysctlcleanup("kern.signosys");
 }
 
 ATF_TP_ADD_TCS(tp)
 {
-	ATF_TP_ADD_TC(tp, sigsys_test);
+	ATF_TP_ADD_TC(tp, sigsys_test_on);
+	ATF_TP_ADD_TC(tp, sigsys_test_off);
 	return (atf_no_error());
 }