Index: lib/libstand/nfs.c
===================================================================
--- lib/libstand/nfs.c
+++ lib/libstand/nfs.c
@@ -223,6 +223,7 @@
 nfs_getrootfh(struct iodesc *d, char *path, u_char *fhp)
 {
 	int len;
+	char *env, *end;
 	struct args {
 		n_long	len;
 		char	path[FNAME_SIZE];
@@ -272,8 +273,14 @@
 	/*
 	 * Improve boot performance over NFS
 	 */
-	if (getenv("nfs.read_size") != NULL)
-		nfs_read_size = strtol(getenv("nfs.read_size"), NULL, 0);
+	if ((env = getenv("nfs.read_size")) != NULL) {
+		nfs_read_size = strtol(env, &end, 0);
+		if (*env == '\0' || *end != '\0') {
+			printf("%s: bad value: \"%s\", defaulting to %d\n",
+			    "nfs.read_size", env, NFSREAD_MIN_SIZE);
+			nfs_read_size = NFSREAD_MIN_SIZE;
+		}
+	}
 	if (nfs_read_size < NFSREAD_MIN_SIZE)
 		nfs_read_size = NFSREAD_MIN_SIZE;
 	if (nfs_read_size > NFSREAD_MAX_SIZE)