"Craftsmen built houses"

Translation: Mafundi walizijenga nyumba

[sad_quails]

I read this as, "Craftsmen built horses" first, and thought, "Wow, they must be really talented craftsmen."

[Phmeza]

It now accepts "...walijenga..."

[Ben837613]

If it accepts an answer without the object infix, why is it part of the lesson?