Cokriging Predict Function "Error in h(simpleError(msg, call))"

[MichaelGAttia]

I tried to do CoKriging using gstat library in R. it works perfectly until the prediction function

CK <- predict(g, Grid)

It gave me this error:

Error in h(simpleError(msg, call)) : error in evaluating the argument 'obj' in selecting a method for function 'coordinates': trying to get slot "bbox" from an object (class "data.frame") that is not an S4 object.