Urbis topo is wrong here : Rue Joseph Dupont - Joseph Dupontstraat 8 don't belong to Hôtel de Lannoy - Huis de Lannoy. 

https://monument.heritage.brussels/fr/Bruxelles_Pentagone/Rue_Joseph_Dupont/6/30216

And clearly indicate here too : (U) https://monument.heritage.brussels/nl/buildings/30242

+ restore nl name (on official inventory named Huis de Lannoy) 