Failed to execute "detect" as Player

Upon attempting the following command hooked up to a clock
/execute @p ~ ~ ~ detect ~ ~-1 ~ wool 0 /setblock ~ ~-1 ~ wool 13
It returns the following:
[21:44:47] Failed to execute 'detect' as Jaywhisker
I have met the requirements of the command, and it worked previously, but now it stops.
Any assistance would be appreciated