Turns out those Lego sets you got your kids for the holidays this year may be a pretty solid investment.

According to an analysis by the Telegraph, Lego sets have grown more in value over the last 15 years than the FTSE 100 stock market or the gold market.

The Telegraph estimates the average Lego set has gained 12 percent in value each year since 2000.

But you’re only going to get that kind of return if the sets are un-opened and un-played with.

And what’s the fun in that?