diff --git a/src/devices/nm-device.c b/src/devices/nm-device.c
index 000d781399..7514fa784b 100644
--- a/src/devices/nm-device.c
+++ b/src/devices/nm-device.c
@@ -16344,6 +16344,8 @@ set_property (GObject *object, guint prop_id,
 		/* construct-only */
 		nm_assert (priv->type == NM_DEVICE_TYPE_UNKNOWN);
 		priv->type = g_value_get_uint (value);
+		nm_assert (priv->type > NM_DEVICE_TYPE_UNKNOWN);
+		nm_assert (priv->type <= NM_DEVICE_TYPE_WIFI_P2P);
 		break;
 	case PROP_LINK_TYPE:
 		/* construct-only */
diff --git a/src/tests/config/nm-test-device.c b/src/tests/config/nm-test-device.c
index c21317692a..3a8ef266e8 100644
--- a/src/tests/config/nm-test-device.c
+++ b/src/tests/config/nm-test-device.c
@@ -75,6 +75,7 @@ nm_test_device_new (const char *hwaddr)
 	return g_object_new (NM_TYPE_TEST_DEVICE,
 	                     NM_DEVICE_IFACE, "dummy",
 	                     NM_DEVICE_PERM_HW_ADDRESS, hwaddr,
+	                     NM_DEVICE_DEVICE_TYPE, NM_DEVICE_TYPE_ETHERNET,
 	                     NULL);
 }