Why does the number of rows change during AIC in R? How to ensure that this doesn't happen?

Question

I\'m trying to find a minimal adequate model using AIC in R. I keep getting the following error: Error in step(model) : number of rows in use has changed: remove mi

Answer 1

I was faced with the same problem but I couldn't use Flodel's solution because I couldn't access the original data because it was computed inside a function. I give here my alternative solution which only uses the model. Let data be the dataset with missing values:

model1<-lm(response~., data=data)
model2<-lm(response~., data=model1$model)
step(model2)

Although this way wastes some computer time, it has the advantage of just using information already contained in the model.