diff --git a/libnm/nm-access-point.c b/libnm/nm-access-point.c
index 67b8550603..d9b1c502ef 100644
--- a/libnm/nm-access-point.c
+++ b/libnm/nm-access-point.c
@@ -170,7 +170,7 @@ nm_access_point_get_bssid (NMAccessPoint *ap)
 {
 	g_return_val_if_fail (NM_IS_ACCESS_POINT (ap), NULL);
 
-	return NM_ACCESS_POINT_GET_PRIVATE (ap)->bssid;
+	return nm_str_not_empty (NM_ACCESS_POINT_GET_PRIVATE (ap)->bssid);
 }
 
 /**
diff --git a/libnm/nm-active-connection.c b/libnm/nm-active-connection.c
index a1636598ac..2f04eff095 100644
--- a/libnm/nm-active-connection.c
+++ b/libnm/nm-active-connection.c
@@ -129,7 +129,7 @@ nm_active_connection_get_id (NMActiveConnection *connection)
 {
 	g_return_val_if_fail (NM_IS_ACTIVE_CONNECTION (connection), NULL);
 
-	return NM_ACTIVE_CONNECTION_GET_PRIVATE (connection)->id;
+	return nm_str_not_empty (NM_ACTIVE_CONNECTION_GET_PRIVATE (connection)->id);
 }
 
 /**
@@ -146,7 +146,7 @@ nm_active_connection_get_uuid (NMActiveConnection *connection)
 {
 	g_return_val_if_fail (NM_IS_ACTIVE_CONNECTION (connection), NULL);
 
-	return NM_ACTIVE_CONNECTION_GET_PRIVATE (connection)->uuid;
+	return nm_str_not_empty (NM_ACTIVE_CONNECTION_GET_PRIVATE (connection)->uuid);
 }
 
 /**
@@ -163,7 +163,7 @@ nm_active_connection_get_connection_type (NMActiveConnection *connection)
 {
 	g_return_val_if_fail (NM_IS_ACTIVE_CONNECTION (connection), NULL);
 
-	return NM_ACTIVE_CONNECTION_GET_PRIVATE (connection)->type;
+	return nm_str_not_empty (NM_ACTIVE_CONNECTION_GET_PRIVATE (connection)->type);
 }
 
 /**
@@ -461,6 +461,7 @@ get_property (GObject *object,
 static gboolean
 demarshal_specific_object_path (NMObject *object, GParamSpec *pspec, GVariant *value, gpointer field)
 {
+	const char *v;
 	char **param = (char **) field;
 
 	/* We have to demarshal this manually, because the D-Bus property name
@@ -471,8 +472,10 @@ demarshal_specific_object_path (NMObject *object, GParamSpec *pspec, GVariant *v
 	if (!g_variant_is_of_type (value, G_VARIANT_TYPE_OBJECT_PATH))
 		return FALSE;
 
+	v = g_variant_get_string (value, NULL);
+
 	g_free (*param);
-	*param = g_variant_dup_string (value, NULL);
+	*param = nm_streq0 (v, "/") ? NULL : g_strdup (v);
 	return TRUE;
 }
 
diff --git a/libnm/nm-device-bond.c b/libnm/nm-device-bond.c
index e5977c6664..0a9fae86a2 100644
--- a/libnm/nm-device-bond.c
+++ b/libnm/nm-device-bond.c
@@ -64,7 +64,7 @@ nm_device_bond_get_hw_address (NMDeviceBond *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_BOND (device), NULL);
 
-	return NM_DEVICE_BOND_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_BOND_GET_PRIVATE (device)->hw_address);
 }
 
 /**
diff --git a/libnm/nm-device-bridge.c b/libnm/nm-device-bridge.c
index 83ad963410..cd885b4afb 100644
--- a/libnm/nm-device-bridge.c
+++ b/libnm/nm-device-bridge.c
@@ -64,7 +64,7 @@ nm_device_bridge_get_hw_address (NMDeviceBridge *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_BRIDGE (device), NULL);
 
-	return NM_DEVICE_BRIDGE_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_BRIDGE_GET_PRIVATE (device)->hw_address);
 }
 
 /**
diff --git a/libnm/nm-device-bt.c b/libnm/nm-device-bt.c
index 2c039d941e..f41b7abd8c 100644
--- a/libnm/nm-device-bt.c
+++ b/libnm/nm-device-bt.c
@@ -65,7 +65,7 @@ nm_device_bt_get_hw_address (NMDeviceBt *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_BT (device), NULL);
 
-	return NM_DEVICE_BT_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_BT_GET_PRIVATE (device)->hw_address);
 }
 
 /**
diff --git a/libnm/nm-device-ethernet.c b/libnm/nm-device-ethernet.c
index 15ca0257e6..966ad2d73e 100644
--- a/libnm/nm-device-ethernet.c
+++ b/libnm/nm-device-ethernet.c
@@ -69,7 +69,7 @@ nm_device_ethernet_get_hw_address (NMDeviceEthernet *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_ETHERNET (device), NULL);
 
-	return NM_DEVICE_ETHERNET_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_ETHERNET_GET_PRIVATE (device)->hw_address);
 }
 
 /**
@@ -86,7 +86,7 @@ nm_device_ethernet_get_permanent_hw_address (NMDeviceEthernet *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_ETHERNET (device), NULL);
 
-	return NM_DEVICE_ETHERNET_GET_PRIVATE (device)->perm_hw_address;
+	return nm_str_not_empty (NM_DEVICE_ETHERNET_GET_PRIVATE (device)->perm_hw_address);
 }
 
 /**
diff --git a/libnm/nm-device-generic.c b/libnm/nm-device-generic.c
index 9dd1c945ec..6bc1336219 100644
--- a/libnm/nm-device-generic.c
+++ b/libnm/nm-device-generic.c
@@ -59,7 +59,7 @@ nm_device_generic_get_hw_address (NMDeviceGeneric *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_GENERIC (device), NULL);
 
-	return NM_DEVICE_GENERIC_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_GENERIC_GET_PRIVATE (device)->hw_address);
 }
 
 /*****************************************************************************/
@@ -69,7 +69,7 @@ get_type_description (NMDevice *device)
 {
 	NMDeviceGenericPrivate *priv = NM_DEVICE_GENERIC_GET_PRIVATE (device);
 
-	return priv->type_description;
+	return nm_str_not_empty (priv->type_description);
 }
 
 static const char *
@@ -150,14 +150,15 @@ get_property (GObject *object,
               GValue *value,
               GParamSpec *pspec)
 {
-	NMDeviceGenericPrivate *priv = NM_DEVICE_GENERIC_GET_PRIVATE (object);
+	NMDeviceGeneric *self = NM_DEVICE_GENERIC (object);
+	NMDeviceGenericPrivate *priv = NM_DEVICE_GENERIC_GET_PRIVATE (self);
 
 	switch (prop_id) {
 	case PROP_HW_ADDRESS:
 		g_value_set_string (value, priv->hw_address);
 		break;
 	case PROP_TYPE_DESCRIPTION:
-		g_value_set_string (value, priv->type_description);
+		g_value_set_string (value, get_type_description ((NMDevice *) self));
 		break;
 	default:
 		G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
diff --git a/libnm/nm-device-infiniband.c b/libnm/nm-device-infiniband.c
index 0f92f8304b..665542881e 100644
--- a/libnm/nm-device-infiniband.c
+++ b/libnm/nm-device-infiniband.c
@@ -61,7 +61,7 @@ nm_device_infiniband_get_hw_address (NMDeviceInfiniband *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_INFINIBAND (device), NULL);
 
-	return NM_DEVICE_INFINIBAND_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_INFINIBAND_GET_PRIVATE (device)->hw_address);
 }
 
 /**
diff --git a/libnm/nm-device-ip-tunnel.c b/libnm/nm-device-ip-tunnel.c
index 6410c48c4d..41748aba10 100644
--- a/libnm/nm-device-ip-tunnel.c
+++ b/libnm/nm-device-ip-tunnel.c
@@ -111,7 +111,7 @@ nm_device_ip_tunnel_get_local (NMDeviceIPTunnel *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_IP_TUNNEL (device), NULL);
 
-	return NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->local;
+	return nm_str_not_empty (NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->local);
 }
 
 /**
@@ -127,7 +127,7 @@ nm_device_ip_tunnel_get_remote (NMDeviceIPTunnel *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_IP_TUNNEL (device), NULL);
 
-	return NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->remote;
+	return nm_str_not_empty (NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->remote);
 }
 
 /**
@@ -192,7 +192,7 @@ nm_device_ip_tunnel_get_input_key (NMDeviceIPTunnel *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_IP_TUNNEL (device), NULL);
 
-	return NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->input_key;
+	return nm_str_not_empty (NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->input_key);
 }
 
 /**
@@ -208,7 +208,7 @@ nm_device_ip_tunnel_get_output_key (NMDeviceIPTunnel *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_IP_TUNNEL (device), NULL);
 
-	return NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->output_key;
+	return nm_str_not_empty (NM_DEVICE_IP_TUNNEL_GET_PRIVATE (device)->output_key);
 }
 
 /**
diff --git a/libnm/nm-device-macvlan.c b/libnm/nm-device-macvlan.c
index 610bdc35f2..a370ed1e67 100644
--- a/libnm/nm-device-macvlan.c
+++ b/libnm/nm-device-macvlan.c
@@ -86,7 +86,7 @@ nm_device_macvlan_get_mode (NMDeviceMacvlan *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_MACVLAN (device), NULL);
 
-	return NM_DEVICE_MACVLAN_GET_PRIVATE (device)->mode;
+	return nm_str_not_empty (NM_DEVICE_MACVLAN_GET_PRIVATE (device)->mode);
 }
 
 /**
@@ -141,7 +141,7 @@ nm_device_macvlan_get_hw_address (NMDeviceMacvlan *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_MACVLAN (device), NULL);
 
-	return NM_DEVICE_MACVLAN_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_MACVLAN_GET_PRIVATE (device)->hw_address);
 }
 
 
diff --git a/libnm/nm-device-olpc-mesh.c b/libnm/nm-device-olpc-mesh.c
index a11050f5b4..c69d0b3748 100644
--- a/libnm/nm-device-olpc-mesh.c
+++ b/libnm/nm-device-olpc-mesh.c
@@ -63,7 +63,7 @@ nm_device_olpc_mesh_get_hw_address (NMDeviceOlpcMesh *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_OLPC_MESH (device), NULL);
 
-	return NM_DEVICE_OLPC_MESH_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_OLPC_MESH_GET_PRIVATE (device)->hw_address);
 }
 
 /**
diff --git a/libnm/nm-device-team.c b/libnm/nm-device-team.c
index 8179bd52f4..0c5383deea 100644
--- a/libnm/nm-device-team.c
+++ b/libnm/nm-device-team.c
@@ -66,7 +66,7 @@ nm_device_team_get_hw_address (NMDeviceTeam *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_TEAM (device), NULL);
 
-	return NM_DEVICE_TEAM_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_TEAM_GET_PRIVATE (device)->hw_address);
 }
 
 /**
@@ -119,7 +119,7 @@ nm_device_team_get_config (NMDeviceTeam *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_TEAM (device), NULL);
 
-	return NM_DEVICE_TEAM_GET_PRIVATE (device)->config;
+	return nm_str_not_empty (NM_DEVICE_TEAM_GET_PRIVATE (device)->config);
 }
 
 static const char *
diff --git a/libnm/nm-device-tun.c b/libnm/nm-device-tun.c
index e4e412f8fe..52ba8fd7da 100644
--- a/libnm/nm-device-tun.c
+++ b/libnm/nm-device-tun.c
@@ -74,7 +74,7 @@ nm_device_tun_get_hw_address (NMDeviceTun *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_TUN (device), NULL);
 
-	return NM_DEVICE_TUN_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_TUN_GET_PRIVATE (device)->hw_address);
 }
 
 /**
@@ -92,7 +92,7 @@ nm_device_tun_get_mode (NMDeviceTun *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_TUN (device), NULL);
 
-	return NM_DEVICE_TUN_GET_PRIVATE (device)->mode;
+	return nm_str_not_empty (NM_DEVICE_TUN_GET_PRIVATE (device)->mode);
 }
 
 /**
diff --git a/libnm/nm-device-vlan.c b/libnm/nm-device-vlan.c
index 7083b24484..b67ad373ca 100644
--- a/libnm/nm-device-vlan.c
+++ b/libnm/nm-device-vlan.c
@@ -66,7 +66,7 @@ nm_device_vlan_get_hw_address (NMDeviceVlan *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_VLAN (device), NULL);
 
-	return NM_DEVICE_VLAN_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_VLAN_GET_PRIVATE (device)->hw_address);
 }
 
 /**
@@ -116,6 +116,7 @@ nm_device_vlan_get_vlan_id (NMDeviceVlan *device)
 static gboolean
 connection_compatible (NMDevice *device, NMConnection *connection, GError **error)
 {
+	NMDeviceVlanPrivate *priv;
 	NMSettingVlan *s_vlan;
 	NMSettingWired *s_wired;
 	const char *setting_hwaddr;
@@ -142,8 +143,10 @@ connection_compatible (NMDevice *device, NMConnection *connection, GError **erro
 	else
 		setting_hwaddr = NULL;
 	if (setting_hwaddr) {
-		if (!nm_utils_hwaddr_matches (setting_hwaddr, -1,
-		                              NM_DEVICE_VLAN_GET_PRIVATE (device)->hw_address, -1)) {
+		priv = NM_DEVICE_VLAN_GET_PRIVATE (device);
+		if (   !priv->hw_address
+		    || !nm_utils_hwaddr_matches (setting_hwaddr, -1,
+		                                 priv->hw_address, -1)) {
 			g_set_error_literal (error, NM_DEVICE_ERROR, NM_DEVICE_ERROR_INCOMPATIBLE_CONNECTION,
 			                     _("The hardware address of the device and the connection didn't match."));
 		}
diff --git a/libnm/nm-device-vxlan.c b/libnm/nm-device-vxlan.c
index 86b5fca8e7..ee356749da 100644
--- a/libnm/nm-device-vxlan.c
+++ b/libnm/nm-device-vxlan.c
@@ -95,7 +95,7 @@ nm_device_vxlan_get_hw_address (NMDeviceVxlan *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_VXLAN (device), NULL);
 
-	return NM_DEVICE_VXLAN_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_VXLAN_GET_PRIVATE (device)->hw_address);
 }
 
 /**
@@ -162,7 +162,7 @@ nm_device_vxlan_get_group (NMDeviceVxlan *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_VXLAN (device), NULL);
 
-	return NM_DEVICE_VXLAN_GET_PRIVATE (device)->group;
+	return nm_str_not_empty (NM_DEVICE_VXLAN_GET_PRIVATE (device)->group);
 }
 
 /**
@@ -178,7 +178,7 @@ nm_device_vxlan_get_local (NMDeviceVxlan *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_VXLAN (device), NULL);
 
-	return NM_DEVICE_VXLAN_GET_PRIVATE (device)->local;
+	return nm_str_not_empty (NM_DEVICE_VXLAN_GET_PRIVATE (device)->local);
 }
 
 /**
@@ -458,6 +458,8 @@ finalize (GObject *object)
 
 	g_free (priv->hw_address);
 	g_clear_object (&priv->parent);
+	g_free (priv->group);
+	g_free (priv->local);
 
 	G_OBJECT_CLASS (nm_device_vxlan_parent_class)->finalize (object);
 }
diff --git a/libnm/nm-device-wifi.c b/libnm/nm-device-wifi.c
index 790ddf4ca6..f705dbd2ea 100644
--- a/libnm/nm-device-wifi.c
+++ b/libnm/nm-device-wifi.c
@@ -100,7 +100,7 @@ nm_device_wifi_get_hw_address (NMDeviceWifi *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_WIFI (device), NULL);
 
-	return NM_DEVICE_WIFI_GET_PRIVATE (device)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_WIFI_GET_PRIVATE (device)->hw_address);
 }
 
 /**
@@ -117,7 +117,7 @@ nm_device_wifi_get_permanent_hw_address (NMDeviceWifi *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_WIFI (device), NULL);
 
-	return NM_DEVICE_WIFI_GET_PRIVATE (device)->perm_hw_address;
+	return nm_str_not_empty (NM_DEVICE_WIFI_GET_PRIVATE (device)->perm_hw_address);
 }
 
 /**
@@ -520,10 +520,7 @@ clean_up_aps (NMDeviceWifi *self, gboolean in_dispose)
 
 	priv = NM_DEVICE_WIFI_GET_PRIVATE (self);
 
-	if (priv->active_ap) {
-		g_object_unref (priv->active_ap);
-		priv->active_ap = NULL;
-	}
+	g_clear_object (&priv->active_ap);
 
 	aps = priv->aps;
 
@@ -722,10 +719,7 @@ state_changed_cb (NMDevice *device, GParamSpec *pspec, gpointer user_data)
 	case NM_DEVICE_STATE_DISCONNECTED:
 	case NM_DEVICE_STATE_FAILED:
 		/* Just clear active AP; don't clear the AP list unless wireless is disabled completely */
-		if (priv->active_ap) {
-			g_object_unref (priv->active_ap);
-			priv->active_ap = NULL;
-		}
+		g_clear_object (&priv->active_ap);
 		_nm_object_queue_notify (NM_OBJECT (device), NM_DEVICE_WIFI_ACTIVE_ACCESS_POINT);
 		priv->rate = 0;
 		_nm_object_queue_notify (NM_OBJECT (device), NM_DEVICE_WIFI_BITRATE);
@@ -764,8 +758,7 @@ access_point_removed (NMDeviceWifi *self, NMAccessPoint *ap)
 	NMDeviceWifiPrivate *priv = NM_DEVICE_WIFI_GET_PRIVATE (self);
 
 	if (ap == priv->active_ap) {
-		g_object_unref (priv->active_ap);
-		priv->active_ap = NULL;
+		g_clear_object (&priv->active_ap);
 		_nm_object_queue_notify (NM_OBJECT (self), NM_DEVICE_WIFI_ACTIVE_ACCESS_POINT);
 
 		priv->rate = 0;
diff --git a/libnm/nm-device-wimax.c b/libnm/nm-device-wimax.c
index e14925f778..98c651d3d6 100644
--- a/libnm/nm-device-wimax.c
+++ b/libnm/nm-device-wimax.c
@@ -91,7 +91,7 @@ nm_device_wimax_get_hw_address (NMDeviceWimax *wimax)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_WIMAX (wimax), NULL);
 
-	return NM_DEVICE_WIMAX_GET_PRIVATE (wimax)->hw_address;
+	return nm_str_not_empty (NM_DEVICE_WIMAX_GET_PRIVATE (wimax)->hw_address);
 }
 
 /**
@@ -300,7 +300,7 @@ nm_device_wimax_get_bsid (NMDeviceWimax *self)
 {
 	g_return_val_if_fail (NM_IS_DEVICE_WIMAX (self), NULL);
 
-	return NM_DEVICE_WIMAX_GET_PRIVATE (self)->bsid;
+	return nm_str_not_empty (NM_DEVICE_WIMAX_GET_PRIVATE (self)->bsid);
 }
 
 static gboolean
diff --git a/libnm/nm-device.c b/libnm/nm-device.c
index b3dc01b20f..228e60b70b 100644
--- a/libnm/nm-device.c
+++ b/libnm/nm-device.c
@@ -996,7 +996,7 @@ nm_device_get_iface (NMDevice *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
-	return NM_DEVICE_GET_PRIVATE (device)->iface;
+	return nm_str_not_empty (NM_DEVICE_GET_PRIVATE (device)->iface);
 }
 
 /**
@@ -1014,7 +1014,7 @@ nm_device_get_ip_iface (NMDevice *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
-	return NM_DEVICE_GET_PRIVATE (device)->ip_iface;
+	return nm_str_not_empty (NM_DEVICE_GET_PRIVATE (device)->ip_iface);
 }
 
 /**
@@ -1048,7 +1048,7 @@ nm_device_get_udi (NMDevice *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
-	return NM_DEVICE_GET_PRIVATE (device)->udi;
+	return nm_str_not_empty (NM_DEVICE_GET_PRIVATE (device)->udi);
 }
 
 /**
@@ -1065,7 +1065,7 @@ nm_device_get_driver (NMDevice *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
-	return NM_DEVICE_GET_PRIVATE (device)->driver;
+	return nm_str_not_empty (NM_DEVICE_GET_PRIVATE (device)->driver);
 }
 
 /**
@@ -1082,7 +1082,7 @@ nm_device_get_driver_version (NMDevice *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
-	return NM_DEVICE_GET_PRIVATE (device)->driver_version;
+	return nm_str_not_empty (NM_DEVICE_GET_PRIVATE (device)->driver_version);
 }
 
 /**
@@ -1099,7 +1099,7 @@ nm_device_get_firmware_version (NMDevice *device)
 {
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
-	return NM_DEVICE_GET_PRIVATE (device)->firmware_version;
+	return nm_str_not_empty (NM_DEVICE_GET_PRIVATE (device)->firmware_version);
 }
 
 /**
@@ -1124,7 +1124,7 @@ nm_device_get_type_description (NMDevice *device)
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
 	if (priv->type_description)
-		return priv->type_description;
+		return nm_str_not_empty (priv->type_description);
 
 	if (NM_DEVICE_GET_CLASS (device)->get_type_description) {
 		desc = NM_DEVICE_GET_CLASS (device)->get_type_description (device);
@@ -1137,7 +1137,7 @@ nm_device_get_type_description (NMDevice *device)
 		typename += 8;
 	priv->type_description = g_ascii_strdown (typename, -1);
 
-	return priv->type_description;
+	return nm_str_not_empty (priv->type_description);
 }
 
 /**
@@ -2084,16 +2084,9 @@ done:
 const char *
 nm_device_get_physical_port_id (NMDevice *device)
 {
-	NMDevicePrivate *priv;
-
 	g_return_val_if_fail (NM_IS_DEVICE (device), NULL);
 
-	priv = NM_DEVICE_GET_PRIVATE (device);
-
-	if (priv->physical_port_id && *priv->physical_port_id)
-		return priv->physical_port_id;
-	else
-		return NULL;
+	return nm_str_not_empty (NM_DEVICE_GET_PRIVATE (device)->physical_port_id);
 }
 
 /**
diff --git a/libnm/nm-ip-config.c b/libnm/nm-ip-config.c
index 97fb0aa926..74db9994f3 100644
--- a/libnm/nm-ip-config.c
+++ b/libnm/nm-ip-config.c
@@ -395,7 +395,7 @@ nm_ip_config_get_gateway (NMIPConfig *config)
 {
 	g_return_val_if_fail (NM_IS_IP_CONFIG (config), NULL);
 
-	return NM_IP_CONFIG_GET_PRIVATE (config)->gateway;
+	return nm_str_not_empty (NM_IP_CONFIG_GET_PRIVATE (config)->gateway);
 }
 
 /**
diff --git a/libnm/nm-manager.c b/libnm/nm-manager.c
index 01ed4fa50a..e490104803 100644
--- a/libnm/nm-manager.c
+++ b/libnm/nm-manager.c
@@ -382,7 +382,7 @@ nm_manager_get_version (NMManager *manager)
 {
 	g_return_val_if_fail (NM_IS_MANAGER (manager), NULL);
 
-	return NM_MANAGER_GET_PRIVATE (manager)->version;
+	return nm_str_not_empty (NM_MANAGER_GET_PRIVATE (manager)->version);
 }
 
 NMState
diff --git a/libnm/nm-vpn-connection.c b/libnm/nm-vpn-connection.c
index 4b96210b46..5780fb3a78 100644
--- a/libnm/nm-vpn-connection.c
+++ b/libnm/nm-vpn-connection.c
@@ -79,7 +79,7 @@ nm_vpn_connection_get_banner (NMVpnConnection *vpn)
 	if (priv->vpn_state != NM_VPN_CONNECTION_STATE_ACTIVATED)
 		return NULL;
 
-	return priv->banner;
+	return nm_str_not_empty (priv->banner);
 }
 
 /**
diff --git a/shared/nm-utils/nm-macros-internal.h b/shared/nm-utils/nm-macros-internal.h
index 0b99b0bf56..26b69bc138 100644
--- a/shared/nm-utils/nm-macros-internal.h
+++ b/shared/nm-utils/nm-macros-internal.h
@@ -265,13 +265,11 @@ _NM_IN_STRSET_streq (const char *x, const char *s)
 
 /*****************************************************************************/
 
-#define nm_str_not_empty(str) \
-	({ \
-		/* implemented as macro to preserve constness */ \
-		typeof (str) __str = (str); \
-		_nm_unused const char *__str_type_check = __str; \
-		((__str && __str[0]) ? __str : ((char *) NULL)); \
-	})
+static inline const char *
+nm_str_not_empty (const char *str)
+{
+	return str && str[0] ? str : NULL;
+}
 
 static inline char *
 nm_strdup_not_empty (const char *str)
diff --git a/src/devices/team/nm-device-team.c b/src/devices/team/nm-device-team.c
index c2654b7bf9..11dcdaa9ec 100644
--- a/src/devices/team/nm-device-team.c
+++ b/src/devices/team/nm-device-team.c
@@ -166,18 +166,28 @@ ensure_teamd_connection (NMDevice *device)
 	return !!priv->tdc;
 }
 
+static const char *
+_get_config (NMDeviceTeam *self)
+{
+	return nm_str_not_empty (NM_DEVICE_TEAM_GET_PRIVATE (self)->config);
+}
+
 static gboolean
 teamd_read_config (NMDevice *device)
 {
 	NMDeviceTeam *self = NM_DEVICE_TEAM (device);
 	NMDeviceTeamPrivate *priv = NM_DEVICE_TEAM_GET_PRIVATE (self);
-	char *config = NULL;
+	const char *config = NULL;
 	int err;
 
 	if (priv->tdc) {
-		err = teamdctl_config_actual_get_raw_direct (priv->tdc, &config);
+		err = teamdctl_config_actual_get_raw_direct (priv->tdc, (char **) &config);
 		if (err)
 			return FALSE;
+		if (!config) {
+			/* set "" to distinguish an empty result from no config at all. */
+			config = "";
+		}
 	}
 
 	if (!nm_streq0 (config, priv->config)) {
@@ -224,7 +234,7 @@ update_connection (NMDevice *device, NMConnection *connection)
 		priv->tdc = NULL;
 	}
 
-	g_object_set (G_OBJECT (s_team), NM_SETTING_TEAM_CONFIG, priv->config, NULL);
+	g_object_set (G_OBJECT (s_team), _get_config (self), NULL);
 }
 
 /*****************************************************************************/
@@ -768,11 +778,10 @@ get_property (GObject *object, guint prop_id,
               GValue *value, GParamSpec *pspec)
 {
 	NMDeviceTeam *self = NM_DEVICE_TEAM (object);
-	NMDeviceTeamPrivate *priv = NM_DEVICE_TEAM_GET_PRIVATE (self);
 
 	switch (prop_id) {
 	case PROP_CONFIG:
-		g_value_set_string (value, priv->config);
+		g_value_set_string (value, _get_config (self));
 		break;
 	default:
 		G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);