Prediction using GAM

Recently I was using GAM and couldn't help noticing
the following incoherence in prediction:

data(gam.data)
data(gam.newdata)
gam.object <- gam(y ~ s(x,6) + z, data=gam.data)
predict(gam.object)[1]

1 
0.8017407

predict(gam.object,data.frame(x=gam.data$x[1],z=gam.data$z[1]))
        1 
0.1668452 

I would expect that using two types of predict
arguments should give me the same results.
When I used this to predict a new data set then it
seems OK:

predict(gam.object,data.frame(x=gam.newdata$x[1],z=gam.newdata$z[1]))
        1 
0.4832136

predict(gam.object,gam.newdata)[1]

1 
0.4832136 

Could anybody explain the strange behavior of
predict.gam function?

Thanks,
Kai