Index: sys/fs/nfsclient/nfs_clport.c
===================================================================
--- sys/fs/nfsclient/nfs_clport.c
+++ sys/fs/nfsclient/nfs_clport.c
@@ -361,7 +361,11 @@
 	struct nfsmount *nmp;
 	struct timespec mtime_save;
 	u_quad_t nsize;
-	int setnsize;
+	int setnsize, error;
+
+	error = 0;
+	setnsize = 0;
+	nsize = 0;
 
 	/*
 	 * If v_type == VNON it is a new node, so fill in the v_type,
@@ -389,6 +393,19 @@
 		np->n_vattr.na_fsid = nap->na_fsid;
 		np->n_vattr.na_mode = nap->na_mode;
 	} else {
+		if (np->n_vattr.na_fileid != 0 &&
+		    np->n_vattr.na_fileid != nap->na_fileid) {
+			printf("newnfs: server '%s' error: fileid changed. "
+			    "fsid %jx:%jx: expected fileid %#jx, got %#jx. "
+			    "(Are you using a broken WAN accelerator?)\n",
+			    nmp->nm_com.nmcom_hostname,
+			    (uintmax_t)nmp->nm_fsid[0],
+			    (uintmax_t)nmp->nm_fsid[1],
+			    (uintmax_t)np->n_vattr.na_fileid,
+			    (uintmax_t)nap->na_fileid);
+			error = EIDRM;
+			goto out;
+		}
 		NFSBCOPY((caddr_t)nap, (caddr_t)&np->n_vattr,
 		    sizeof (struct nfsvattr));
 	}
@@ -419,8 +436,6 @@
 	} else
 		vap->va_fsid = vp->v_mount->mnt_stat.f_fsid.val[0];
 	np->n_attrstamp = time_second;
-	setnsize = 0;
-	nsize = 0;
 	if (vap->va_size != np->n_size) {
 		if (vap->va_type == VREG) {
 			if (dontshrink && vap->va_size < np->n_size) {
@@ -490,14 +505,16 @@
 				vaper->va_mtime = np->n_mtim;
 		}
 	}
+
+out:
 #ifdef KDTRACE_HOOKS
 	if (np->n_attrstamp != 0)
-		KDTRACE_NFS_ATTRCACHE_LOAD_DONE(vp, vap, 0);
+		KDTRACE_NFS_ATTRCACHE_LOAD_DONE(vp, vap, error);
 #endif
 	NFSUNLOCKNODE(np);
 	if (setnsize)
 		vnode_pager_setsize(vp, nsize);
-	return (0);
+	return (error);
 }
 
 /*