ᐅ Sealing or filling the basement stairs from the house side

Hello,

the area around my basement stairs has just been plastered.

I noticed that the basement stairs are flush with the basement wall/plaster at the bottom, but at the top there is a gap of about a finger’s width.

Is this normal / can this happen sometimes?

How can I “fill” this so that dirt, small stones, and debris don’t accumulate there over time?

Best regards and many thanks!

In our case, it is different. The staircase is directly connected to the concrete.