diff --git a/src/devices/wwan/nm-device-modem.c b/src/devices/wwan/nm-device-modem.c
index b79d145d1f..ccf6e17da2 100644
--- a/src/devices/wwan/nm-device-modem.c
+++ b/src/devices/wwan/nm-device-modem.c
@@ -743,9 +743,10 @@ dispose (GObject *object)
 {
 	NMDeviceModemPrivate *priv = NM_DEVICE_MODEM_GET_PRIVATE ((NMDeviceModem *) object);
 
-	if (priv->modem)
+	if (priv->modem) {
 		g_signal_handlers_disconnect_by_data (priv->modem, NM_DEVICE_MODEM (object));
-	g_clear_object (&priv->modem);
+		g_clear_object (&priv->modem);
+	}
 
 	G_OBJECT_CLASS (nm_device_modem_parent_class)->dispose (object);
 }
diff --git a/src/devices/wwan/nm-modem.c b/src/devices/wwan/nm-modem.c
index d87cf6c1d2..5de461e5d8 100644
--- a/src/devices/wwan/nm-modem.c
+++ b/src/devices/wwan/nm-modem.c
@@ -1097,7 +1097,10 @@ deactivate_cleanup (NMModem *self, NMDevice *device)
 
 	priv->in_bytes = priv->out_bytes = 0;
 
-	g_clear_object (&priv->ppp_manager);
+	if (priv->ppp_manager) {
+		g_signal_handlers_disconnect_by_data (priv->ppp_manager, self);
+		g_clear_object (&priv->ppp_manager);
+	}
 
 	if (device) {
 		g_return_if_fail (NM_IS_DEVICE (device));