Drag and Drop a game object into public field in inspector

Hello,

I’m a total noob and just started learning C#.
I watched all the beginner videos for programming with unity and now I wanted to try some stuff trial and error style.

I have the following problem now:
I attached a script to my FirstPersonCharacter. In that script, the only thing that I wrote was “public GameObject gun;” which I can also see in the inspector now.

I created a Cylinder and I wanted to drag this object into that field in the inspector, but it just won’t attach.
Why?

edit: here’s a picture:

Imgur

You have a script called GameObject. That may the problem.

You were perfectly right, thank you!