No error on uploading to wrong board

[NicoHood]

If you want to upload a Uno sketch to a leonardo board it compiles and uploads.
In debugging mode it sais

avrdude: Device signature = 0xffffff (retrying)

Reading | ################################################## | 100% 0.03s

avrdude: Device signature = 0xffffff (retrying)

Reading | ################################################## | 100% 0.03s

avrdude: Device signature = 0xffffff
avrdude: Yikes!  Invalid device signature.
         Double check connections and try again, or use -F to override
         this check.


avrdude done.  Thank you.

But in the IDE it still sais "Uploading..." without any error (its still blue, not red).
Using IDE 1.6 Win 7/8