BTIG analyst Mark Palmer reiterated his sell rating on Square Inc. SQ, -0.43% shares Tuesday, writing that share price fluctuations in recent months have been similar to Bitcoin BTCUSD, -2.04% price fluctuations, though that's not the main reason for his caution. "While that connection seems to have worked to Square's benefit during the latter portion of that ride given that Bitcoin has been rallying, it served as confirmation that Square's stock has become tethered to the movements of a volatile cryptocurrency - a live-with-it, die-with-it relationship that we do not believe is conducive to the sustenance of a lofty multiple," Palmer wrote. He's one of two analysts with a sell rating on Square's stock, according to FactSet, and his concerns stem mainly from Square's valuation, with shares trading at nearly 26 times consensus estimates for adjusted Ebitda in 2020. "Its valuation already reflects unimpeded rapid growth when competitive, credit-related and macro factors that could moderate the pace of its expansion remain very much in play," Palmer added. Square shares are up 3.5% in Tuesday trading and 215% over the past 12 months, while the S&P 500 Index SPX, -1.11% is up 16% over the past year.