You should be nervous when the press gets worked into a lather over stocks instead of companies. The latest case in point is the race to the first $1 trillion market cap. A simple Google search will turn up dozens of articles that pay more attention to the race instead of the actual fundamentals of the businesses.

This giddy atmosphere is reminiscent of the froth leading up to the dot.com crash and it’s a particularly relevant example since Microsoft (NSDQ: MSFT) is once again in the $1 trillion running. If you think back to 1999, people were saying the same thing about MSFT, only to have it bomb out three months after its valuation peaked just shy of $620 billion. I’m not sure if there’s a trillion dollar curse, but it sure seems like a suspicious coincidence.

The good news is that, unlike the days of the dot com bubble, tech companies today actually do have the technology that justifies their big market caps. Five tech companies have valuations over $400 billion: Apple (NSDQ: AAPL), with $822.5 billion; Alphabet (NSDQ: GOOGL), $656.6 billion; Microsoft, $521.9 billion; Amazon (NSDQ: AMZN), $464.4 billion; and Facebook, $436.7 billion. All of these companies have sound businesses. They all have products they’re actually selling, unlike in the bad old days of the early aughts when many didn’t. They’ve also been investing heavily in developing next generation technologies, notably virtual reality, artificial intelligence and machine learning. I don’t think any of these five would be bad investments, in and of themselves.

Apple probably stands the best chance of crossing the $1 trillion finishing line, and not just because it’s already within spitting distance. It’s made several smart acquisitions, most recently picking up Lattice, which specializes in making sense of unorganized, dark data. Apple last year also picked up Turi, which specializes in machine learning. If Apple manages to reboot lagging iPhone sales, gets a bump from any congressional tax deal and continues innovating technologically, it could pass the trillion-dollar threshold.

But generally speaking, you must buy the business, not the hype. And I see warning signs developing in the economic outlook that are worrying.

The biggest red flag is bank resolutions. It seems an obscure metric, but the FDIC doesn’t takeover banks on a whim; those banks have to be in serious trouble. Banks usually get into trouble by making bad loans and that usually happens when, to maintain growth, they make those loans to marginal borrowers.

Credit has been easy for so long, most of the best qualified borrowers already have all the cash they need, so banks have started making loans to folks that might not have the best means of paying them back. When that happens, it’s a good sign that credit has expanded a bit too much. It’s only the middle of May and there already have been five bank failures, as many as there were in all of 2016.

The VIX index also makes me worry, precisely because it’s telling me not to. An indicator of the market’s expected volatility over the next 30 days, the VIX recently hit a ten-year low. Maybe it’s because I’m the naturally cautious type, but I just can’t see how that’s possible with everything going on in the world. The sentiment seems more like complacency than optimism.

Considering that a lot of these $1 trillion dollar hopes are pinned on a tax reform deal getting done in Congress, a failure there could force investors to start digging deeper into the overall state of the economy. Accordingly, trends such as the rise in bank failures will get more attention and people will start to realize that maybe they shouldn’t be quite so calm. That sounds like the makings of a sell-off to me.

If you’ve bought into a stock like Apple or Amazon just because it looks like it could be the first to hit a $1 trillion valuation, odds are you’ll be tempted to duck out at the first sign of trouble. If you bought them because they’re good businesses with promising technologies and growth prospects, you should treat a sell-off as an opportunity to buy more.