I was going through some problems of chirality when I came across the following compound

Is the given compound chiral?

My attempt

If we look at its mirror image about a mirror which is perpendicular to plane of the molecule, the two $CH_3 $ groups which is pointing upwards and downwards(implied by the wedge and the dash) will interchange their positions but then also the mirror image would be perfectly superimposable on the given compound.Hence it should be achiral but the answer key gives it to be chiral.I couldn't get it.Is this compound an exception?Thanks.