Apple (AAPL - Get Report)  shares are in for a dip ahead of its much-hyped iPhone 8 unveiling event on Sept. 12 and expected launch date of Sept. 22. 

"I'm surprised Apple shares haven't dipped already," Loup Ventures founder Gene Munster said. "I would expect a pullback in the next few weeks or month."

Shares of Apple were trading up slightly to $163.30 in morning trading on Wednesday. 

While common sense would make you think the stock would shoot up around an iPhone release date, Apple shares have historically risen in anticipation of a new iPhone model, and then suddenly dipped right before the actual release date in mid-September.

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Why is that? Munster said it's because investors don't want to wait to see if the stock goes even higher after the product comes out and is reviewed. They would rather be safe and take the profits they've gleaned from the hype-driven rise the stock gets ahead of the launch date.

This year's 10th-anniversary edition of the iPhone is expected to go on sale on Sept. 22 because the device has historically been released 10 days after the unveiling event, which will take place Sept. 12 this year. Based on the history of Apple shares, they should advance in the first weeks of September, dip a few days before the release date, and then rise again.

Take a look at this chart showing Apple's stock in September 2016. The iPhone 7 and iPhone 7 Plus came out on September 16, 2016, which is indicated by an arrow. Notice shares were sold up until a few days before the release date when they started to dip due to profit-taking. 

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The chart below shows Apple's stock in September 2014. The iPhone 6 came out September 19, 2014, where the arrow is hovering on the chart. Notice again the slight dip in shares in the few days before the release date. 

Apple's stock has already risen an impressive 40% year-to-date and the stock is up about 10% in the past month. Many Apple investors will argue that it's best to take a long-term view on Apple. While the stock has momentary dips as seen in the charts above, the stock is up more than 70% in the past five years.

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Editors' pick: Originally published Aug. 25.