Federal trademark registration helps protect the hundreds of billions of dollars of brand value that trademarks can represent. Recently, interest in the failure-to-function doctrine, which prevents registration of proposed trademarks that consumers do not perceive as marks, has surged at the appellate body of the United States Patent and Trademark Office (USPTO), the Trademark Trial and Appeal Board (TTAB). This Note is the first in-depth, focused critique of the TTAB’s recent failure-to-function jurisprudence. It argues that, as the TTAB currently uses it, the failure-to-function doctrine is incoherent and lacks clarity. On a more granular level, the doctrine rests on inconsistent multifactor tests whose factors the TTAB adds, subtracts, modifies, reconceptualizes, and weighs differently across cases, giving the USPTO little meaningful criteria by which to decide what marks merit registration. This inconsistency risks increasing costs for the USPTO, brands, and consumers by creating uncertainty as to what proposed trademarks the USPTO will approve. In response, this Note proposes combining failure to function with a different trademark doctrine: the doctrine of aesthetic functionality. Replacing failure to function’s unwieldy multifactor inquiries with aesthetic functionality’s narrow focus on competition promises to increase clarity and, in so doing, mitigate or avoid costs to the USPTO, brands, and consumers.