Index: add.R
===================================================================
--- add.R	(revision 54562)
+++ add.R	(working copy)
@@ -330,7 +330,7 @@
 drop1.default <- function(object, scope, scale = 0, test=c("none", "Chisq"),
 			  k = 2, trace = FALSE, ...)
 {
-    tl <- attr(object$terms, "term.labels")
+    tl <- attr(terms(object), "term.labels")
     if(missing(scope)) scope <- drop.scope(object)
     else {
 	if(!is.character(scope))
@@ -344,7 +344,7 @@
     ans <- matrix(nrow = ns + 1L, ncol = 2L,
                   dimnames =  list(c("<none>", scope), c("df", "AIC")))
     ans[1, ] <- extractAIC(object, scale, k = k, ...)
-    n0 <- length(object$residuals)
+    n0 <- length(residuals(object))
     env <- environment(formula(object))
     for(i in seq(ns)) {
 	tt <- scope[i]
@@ -356,7 +356,7 @@
                        evaluate = FALSE)
 	nfit <- eval(nfit, envir=env) # was  eval.parent(nfit)
 	ans[i+1, ] <- extractAIC(nfit, scale, k = k, ...)
-        if(length(nfit$residuals) != n0)
+        if(length(residuals(nfit)) != n0)
             stop("number of rows in use has changed: remove missing values?")
     }
     dfs <- ans[1L , 1L] - ans[, 1L]