The risk of Acacia Communications, Inc. (NASDAQ:ACIA)’s overreliance on a few customers for most of its revenue has once again come to the fore, sparking a selloff in the stock. It turns out that two of Acacia’s five largest customers are having growth problem. Acacia depends on five of its largest customers for more than 82% of its revenue, according to the company’s regulatory filing for 1H2016.

ZTE posts topline miss

ZTE Group, Acacia’s largest customer, posted 3Q16 top-line results that fell short of expectations. The Chinese company reported 3Q revenue of 23.8 billion yuan, up 5.23% YoY. Despite the growth, the top-line figure missed the consensus estimate of 26.3 billion yuan. Given that ZTE accounted for close to 38% of Acacia’s revenue in 1H2016, the revenue miss has caused concern among Acacia investors.

Fears are also mounting that U.S. ban on ZTE products could be starting to take a hit on the company’s growth. ZTE’s problem with the U.S. stemmed from the company’s move to sell its equipment to Iran against U.S. sanctions.

Besides the ban, ZTE could start seeing a slowdown in the demand for its 4G equipment as majority of 4G network build-outs near completion in key markets. Strong demand for 4G systems amid a race by carriers and other providers to upgrade their networks helped fuel growth at ZTE.

ADVA issues soft 4Q guidance

Other than ZTE, ADVA Optical Networking, Acacia’s second-largest customer, guided softly for 4Q. The German company is expecting 4Q revenue in the band of 125 to 140 million euros. However, the consensus estimate calls for revenue of at least 149 million euros.

Given the position ADVA holds in Acacia’s order book, investors fear that if the company is facing growth problems, its supplier Acacia would face growth problems as well.

Acacia stock crashed almost 16% in the last session to close at $73.66. However, the stock is still up nearly 140% YTD.