diff --git a/phc2sys.c b/phc2sys.c
index 3f5d144..224c03e 100644
--- a/phc2sys.c
+++ b/phc2sys.c
@@ -1324,6 +1324,11 @@ int main(int argc, char *argv[])
 		goto bad_usage;
 	}
 
+	if (node.servo_type == CLOCK_SERVO_NTPSHM) {
+		node.kernel_leap = 0;
+		node.sanity_freq_limit = 0;
+	}
+
 	print_set_progname(progname);
 	print_set_verbose(verbose);
 	print_set_syslog(use_syslog);
diff --git a/ptp4l.c b/ptp4l.c
index a33900f..25270c6 100644
--- a/ptp4l.c
+++ b/ptp4l.c
@@ -300,6 +300,10 @@ int main(int argc, char *argv[])
 	    ds->flags & DDS_SLAVE_ONLY) {
 		ds->clockQuality.clockClass = 255;
 	}
+	if (cfg_settings.clock_servo == CLOCK_SERVO_NTPSHM) {
+		cfg_settings.dds.kernel_leap = 0;
+		cfg_settings.dds.sanity_freq_limit = 0;
+	}
 
 	print_set_progname(progname);
 	print_set_verbose(cfg_settings.verbose);