Many epistemologists hold that the Zebra Deduction (the animals are zebras, so they aren't cleverly disguised mules) fails to transmit knowledge to its conclusion, but there is little agreement concerning why it has this defect. A natural idea is, roughly, that it fails to transmit because it fails to improve the safety of its conclusion. In his ‘Transmission Failure Explained’, Martin Smith defends a transmission principle which is supposed to underwrite this natural idea. There are two problems with Smith's account. First, Smith's argument for his transmission principle relies on a dubious premise (§1). Second, even if his transmission principle is true, Smith shows neither that it prevents the Zebra Deduction from transmitting knowledge to its conclusion, nor that it secures the natural idea (§2). I suspect that the failures of Smith's account will be instructive for anyone who wants to connect transmission failure with a failure to enhance the safety, reliability or probability of one's conclusion.