Bug in polyfit


I'm using matplotlib 0.71 and I think I found a bug in polyfit.

This simple linear regression on two data points gives the correct answer:
>>> polyfit([731.924,731.988],[915,742],1)
array([ -2703.12505517, 1979397.10294428])

However, if I multiply my x values by 1000 the result is wrong:
>>> polyfit([731924,731988],[915,742],1)
array([ 5.17650790e-009, 8.28496211e+002])

Could that be some kind of overflow problem ???