Enter/exit nether, server reports: <player> moved too quickly

Not a big deal, but when I enter/exit the nether, the server reports things like this:

[20:30:17] [Server thread/INFO]: [STDOUT]: from = OVERWORLD
[20:30:17] [Server thread/INFO]: [STDOUT]: to = NETHER
[20:30:18] [Server thread/WARN]: theosib moved too quickly! -340.0,20.0,-184.83860101603622

[20:31:27] [Server thread/INFO]: [STDOUT]: from = NETHER
[20:31:27] [Server thread/INFO]: [STDOUT]: to = OVERWORLD
[20:31:28] [Server thread/WARN]: theosib moved too quickly! 168.81978364454065,35.0,150.44566923981205