Why does 737 autopilot override to Mach speed?

Every time I use the 737 autopilot to ascend to cruising altitude, when it gets to around 25,000 ft, it switches my speed from IAS to Mach, which is usually slower than the IAS speed I set.

Any way to stop this? It’s quite annoying.

Quote from Overloaded

You can change the laws of physics.

Look up altitude, temperature and the speed of sound. Above about 30,000 the speed must drop as the (falling) speed of sound becomes predominant so climbing at a Mach No. means a lowering Indicated Airspeed. Have a peep at True or Ground Speed though.

I know that but why does the autopilot switch from 265 IAS to 0.65 Mach speed automatically? That’s a reduction equivalent to 254 IAS at the altitude I was at earlier.

Quote from Overloaded

You are not allowed to overspeed the plane. The 747 was a hot rod but the 737 was modest, look at the wing sweep angle.

265 IAS is overspeed at 28,000 ft???

I think it was only 420-430 knots?

Quote from Jet-Pack (IPACS)

This is a real world feature. Above roughly 25,000ft basically all airliners use Mach number, not IAS because that becomes the limiting flight envelope parameter. The max airspeed is then dictated by the maximum Mach number.

At the cross over altitude the aircraft switches from indicated airspeed to Mach number to prevent an overspeed situation. It actually keeps you safe.

What would you recommend setting the IAS speed at through 25,000 ft?