--- top/top.c
+++ top/top.c	2012-07-05 07:51:02.384012773 +0000
@@ -1151,9 +1151,15 @@ static const char *user_certify (WIN_t *
    Monpidsidx = 0;
    if (*str) {
       num = (uid_t)strtoul(str, &endp, 0);
-      if ('\0' == *endp)
+      if ('\0' == *endp) {
          pwd = getpwuid(num);
-      else
+         if (!pwd) {
+            /* Allow foreign users from e.g. within chroot environment */
+            q->usrseluid = num;
+            q->usrseltyp = typ;
+            return NULL;
+	 }
+      } else
          pwd = getpwnam(str);
       if (!pwd) return N_txt(BAD_username_txt);
       q->usrseluid = pwd->pw_uid;