diff --git a/ip/ipnetns.c b/ip/ipnetns.c
index fc58a04b..46cc235b 100644
--- a/ip/ipnetns.c
+++ b/ip/ipnetns.c
@@ -137,7 +137,7 @@ int get_netnsid_from_name(const char *name)
 	parse_rtattr(tb, NETNSA_MAX, NETNS_RTA(rthdr), len);
 
 	if (tb[NETNSA_NSID]) {
-		ret = rta_getattr_u32(tb[NETNSA_NSID]);
+		ret = rta_getattr_s32(tb[NETNSA_NSID]);
 	}
 
 out:
@@ -161,9 +161,13 @@ static struct hlist_head	name_head[NSIDMAP_SIZE];
 
 static struct nsid_cache *netns_map_get_by_nsid(int nsid)
 {
-	uint32_t h = NSID_HASH_NSID(nsid);
 	struct hlist_node *n;
+	uint32_t h;
 
+	if (nsid < 0)
+		return NULL;
+
+	h = NSID_HASH_NSID(nsid);
 	hlist_for_each(n, &nsid_head[h]) {
 		struct nsid_cache *c = container_of(n, struct nsid_cache,
 						    nsid_hash);
@@ -178,6 +182,9 @@ char *get_name_from_nsid(int nsid)
 {
 	struct nsid_cache *c;
 
+	if (nsid < 0)
+		return NULL;
+
 	netns_nsid_socket_init();
 	netns_map_init();
 
@@ -266,6 +273,9 @@ static int netns_get_name(int nsid, char *name)
 	DIR *dir;
 	int id;
 
+	if (nsid < 0)
+		return -EINVAL;
+
 	dir = opendir(NETNS_RUN_DIR);
 	if (!dir)
 		return -ENOENT;
@@ -277,7 +287,7 @@ static int netns_get_name(int nsid, char *name)
 			continue;
 		id = get_netnsid_from_name(entry->d_name);
 
-		if (nsid == id) {
+		if (id >= 0 && nsid == id) {
 			strcpy(name, entry->d_name);
 			closedir(dir);
 			return 0;
@@ -317,20 +327,20 @@ int print_nsid(struct nlmsghdr *n, void *arg)
 	if (n->nlmsg_type == RTM_DELNSID)
 		print_bool(PRINT_ANY, "deleted", "Deleted ", true);
 
-	nsid = rta_getattr_u32(tb[NETNSA_NSID]);
+	nsid = rta_getattr_s32(tb[NETNSA_NSID]);
 	if (nsid < 0)
-		print_string(PRINT_ANY, "nsid", "nsid %s ", "not-assigned");
+		print_string(PRINT_FP, NULL, "nsid unassigned ", NULL);
 	else
-		print_uint(PRINT_ANY, "nsid", "nsid %u ", nsid);
+		print_int(PRINT_ANY, "nsid", "nsid %d ", nsid);
 
 	if (tb[NETNSA_CURRENT_NSID]) {
-		current = rta_getattr_u32(tb[NETNSA_CURRENT_NSID]);
+		current = rta_getattr_s32(tb[NETNSA_CURRENT_NSID]);
 		if (current < 0)
-			print_string(PRINT_ANY, "current-nsid",
-				     "current-nsid %s ", "not-assigned");
+			print_string(PRINT_FP, NULL,
+				     "current-nsid unassigned ", NULL);
 		else
-			print_uint(PRINT_ANY, "current-nsid",
-				   "current-nsid %u ", current);
+			print_int(PRINT_ANY, "current-nsid",
+				  "current-nsid %d ", current);
 	}
 
 	c = netns_map_get_by_nsid(tb[NETNSA_CURRENT_NSID] ? current : nsid);
@@ -340,7 +350,7 @@ int print_nsid(struct nlmsghdr *n, void *arg)
 		netns_map_del(c);
 	}
 
-	/* During 'ip monitor nsid', no chance to have new nsid in cache. */
+	/* nsid might not be in cache */
 	if (c == NULL && n->nlmsg_type == RTM_NEWNSID)
 		if (netns_get_name(nsid, name) == 0) {
 			print_string(PRINT_ANY, "name",
@@ -429,10 +439,10 @@ static int netns_list_id(int argc, char **argv)
 			NEXT_ARG();
 
 			if (get_integer(&filter.target_nsid, *argv, 0))
-				invarg("\"target-nsid\" value is invalid\n",
+				invarg("\"target-nsid\" value is invalid",
 				       *argv);
 			else if (filter.target_nsid < 0)
-				invarg("\"target-nsid\" value should be >= 0\n",
+				invarg("\"target-nsid\" value should be >= 0",
 				       argv[1]);
 		} else if (strcmp(*argv, "nsid") == 0) {
 			if (nsid >= 0)
@@ -440,9 +450,9 @@ static int netns_list_id(int argc, char **argv)
 			NEXT_ARG();
 
 			if (get_integer(&nsid, *argv, 0))
-				invarg("\"nsid\" value is invalid\n", *argv);
+				invarg("\"nsid\" value is invalid", *argv);
 			else if (nsid < 0)
-				invarg("\"nsid\" value should be >= 0\n",
+				invarg("\"nsid\" value should be >= 0",
 				       argv[1]);
 		} else
 			usage();
@@ -491,8 +501,7 @@ static int netns_list(int argc, char **argv)
 		if (ipnetns_have_nsid()) {
 			id = get_netnsid_from_name(entry->d_name);
 			if (id >= 0)
-				print_uint(PRINT_ANY, "id",
-					   " (id: %d)", id);
+				print_int(PRINT_ANY, "id", " (id: %d)", id);
 		}
 		print_string(PRINT_FP, NULL, "\n", NULL);
 		close_json_object();
@@ -923,9 +932,9 @@ static int netns_set(int argc, char **argv)
 	if (strcmp(argv[1], "auto") == 0)
 		nsid = -1;
 	else if (get_integer(&nsid, argv[1], 0))
-		invarg("Invalid \"netnsid\" value\n", argv[1]);
+		invarg("Invalid \"netnsid\" value", argv[1]);
 	else if (nsid < 0)
-		invarg("\"netnsid\" value should be >= 0\n", argv[1]);
+		invarg("\"netnsid\" value should be >= 0", argv[1]);
 
 	snprintf(netns_path, sizeof(netns_path), "%s/%s", NETNS_RUN_DIR, name);
 	netns = open(netns_path, O_RDONLY | O_CLOEXEC);