If you own a NASDAQ-100 index fund, you might soon be forced to buy SpaceX stock whether you like it or not - and at prices that could make Wall Street blush.

According to investor discussions gaining traction on Reddit, SpaceX (which has acquired xAI, which itself acquired X) is negotiating with NASDAQ to change its index inclusion rules as a condition for going public. The company is reportedly aiming for a valuation around $1.75 trillion.

Here's where it gets interesting for passive investors. Under the proposed rule changes, SpaceX could float only 5% of its shares at IPO while getting weighted in the index as if it had a much larger public float. The math works like this: a 5% float at $1.75 trillion market cap would normally represent $87.5 billion in tradable shares. But the new rules would apply a 5x multiplier to companies with less than 20% float, giving SpaceX an index weight of roughly $437 billion.

Why does this matter? Because every index fund tracking the NASDAQ-100 would be forced to buy SpaceX shares based on that inflated weighting. Another rule change would allow the stock to join the index after just 15 days if it ranks among the top 40 companies - effectively creating a captive buyer base for early shareholders looking to exit.

"This is a masterclass in financial engineering," one investor wrote on the r/stocks subreddit. "Private shareholders get to unload at peak prices to index funds that have no choice but to buy."

To be clear, these rule changes haven't been officially confirmed by NASDAQ, and the source is Reddit investor discussion rather than a regulatory filing. But if true, it would create a scenario where your retirement account could be buying into a barely-public company at a valuation set by insiders, not the open market.

The proposed mechanics are troubling for anyone who believes in price discovery. Traditional IPOs force companies to float enough shares that the market - not the founder - determines what the stock is worth. By gaming the index inclusion rules, SpaceX could bypass that process entirely.

For passive investors, the lesson is simple: just because something is in your index fund doesn't mean it's a good investment. Index inclusion has become a feature you can lobby for, not just a milestone you earn.

If these rule changes go through, you might want to check whether your NASDAQ-100 fund is about to become a very expensive SpaceX shareholder on your behalf.