Tesla (TSLA) CEO Elon Musk admits he has learned a lot in the dozen years since Aston Martin's (AML.L) chief slammed him for being an "amateur car builder."

The revelation from Musk came in a tweet on Wednesday evening when the car genius was asked about his 2008 visit to an Aston Martin factory.

While Musk replied that the Aston Martin CEO at the time, Dr. Ulrich Bez, was “quite grumpy,” he also admitted, “We did not actually know what we were doing, so he had a point.”

Author Ashlee Vance also confirmed Bez’s impression of Musk in her book “Elon Musk: Tesla, SpaceX and the Quest for a Fantastic Future,” where he wrote about the visit between the two CEOs.

Vance detailed how Palmer treated Musk “like an amateur car builder” as he visited Aston Martin to tour the factory, Business Insider reported.

In over a decade since the meeting, Musk admitted to Tesla’s shortcomings at the time – a car company that has often struggled to gain a foothold in EV market. Now, as the automaker enters the S&P, it proves how far Tesla has come and how much Musk has learned along the way.

But Tesla has not been alone in its challenges as Aston Martin has fought many uphill battles in its 100-year history.

The car company has filed bankruptcy seven times, announced pre-tax losses of 53% in 2019 ($134 million), pulled out of the electric car business in January 2020, and has recently seen its share price drop on the shakiness of Brexit.

Aston Martin sold 5,862 vehicles in 2019, while Tesla delivered 367,500 vehicles for the year.

Shares of Tesla shares were trading at $626.80 as of premarket open, up $4.03 or 0.65% while shares of Aston Martin were trading at $1,700, down $6.20 or 0.36% at the same time.

Tesla CEO Elon Musk visited the factory site outside Berlin in September
Tesla CEO Elon Musk visited the factory site outside Berlin. AFP / Odd ANDERSEN