diff --git a/us.c b/us.c
index 04e1bf9..8b752b6 100644
--- a/us.c
+++ b/us.c
@@ -158,6 +158,10 @@ int main(int argc, char *argv[])
 	if (!t_pw)
 		die("user_to_passwd:");
 	t_gr = group_to_grp(t_grp, &t_gr_info);
+	gid_t t_groups[GROUPS_MAX];
+	int nt_groups = GROUPS_MAX;
+	if (getgrouplist(t_pw->pw_name, t_pw->pw_gid, t_groups, &nt_groups) == -1)
+		die("getgrouplist:");
 
 	/* Don't have to wait for children */
 	struct sigaction sa = {0};
@@ -186,6 +190,7 @@ int main(int argc, char *argv[])
 		struct user_info who_info = {0}, as_info = {0};
 		int who_usr = conf[i].who[0] == ':' ? 0 : 1;
 		int as_usr = conf[i].as[0] == ':' ? 0 : 1;
+
 		if (who_usr) {
 			who_pw = user_to_passwd(conf[i].who, &who_info);
 			if (!who_pw)
@@ -193,13 +198,13 @@ int main(int argc, char *argv[])
 			if (my_pw->pw_uid != who_pw->pw_uid)
 				continue;
 		} else {
-			who_gr = group_to_grp(conf[i].who, &who_info);
+			who_gr = group_to_grp(conf[i].who+1, &who_info);
 			if (!who_gr)
 				die("%s not a valid group", conf[i].who);
 			gid_t w_gid = who_gr->gr_gid;
 			int x = 0;
 			for (; x < n_groups && w_gid != my_groups[x]; x++);
-			if (w_gid != my_groups[x])
+			if (x == n_groups)
 				continue;
 		}
 
@@ -209,14 +214,15 @@ int main(int argc, char *argv[])
 				die("%s not a valid user", conf[i].as);
 			if (t_pw->pw_uid != as_pw->pw_uid)
 				continue;
-		} else if (t_gr) {
-			as_gr = group_to_grp(conf[i].as, &as_info);
+		} else {
+			as_gr = group_to_grp(conf[i].as+1, &as_info);
 			if (!as_gr)
 				die("%s not a valid group", conf[i].as);
-			if (t_gr->gr_gid != as_gr->gr_gid)
+			gid_t a_gid = as_gr->gr_gid;
+			int x = 0;
+			for (; x < nt_groups && a_gid != t_groups[x]; x++);
+			if (x == nt_groups)
 				continue;
-		} else {
-			continue;
 		}
 		here = 1;
 		if (conf[i].type == 0)
@@ -382,7 +388,7 @@ static inline void usage(int complete)
 	       "-e        keep the user's entire environment\n"
 	       "-A        use the command in US_ASKPASS as askpass helper\n"
 	       "-u user   set new user to 'user' instead of root\n"
-	       "-s group  set new group to 'group'\n"
+	       "-g group  set new group to 'group'\n"
 	       "-C config use specifi config file\n");
 }
 
@@ -746,7 +752,7 @@ static int get_config(struct config **conf, int *num)
 		struct config c = {0};
 		for (s = line;; s = NULL, n++) {
 			int getflags = 0;
-			if (!(t = strtok_r(s, " ", &sv)))
+			if (!(t = strtok_r(s, " \t", &sv)))
 				break;
 			if (*t == '#')
 				break;