diff --git a/cmd/zfs/zfs_main.c b/cmd/zfs/zfs_main.c
index 5e7ee0f5b7bd..224ed16048b0 100644
--- a/cmd/zfs/zfs_main.c
+++ b/cmd/zfs/zfs_main.c
@@ -5238,10 +5238,17 @@ parse_fs_perm(fs_perm_t *fsperm, nvlist_t *nvl)
 					break;
 				}
 
-				if (nice_name != NULL)
+				if (nice_name != NULL) {
 					(void) strlcpy(
 					    node->who_perm.who_ug_name,
 					    nice_name, 256);
+				} else {
+					/* User or group unknown */
+					(void) snprintf(
+					    node->who_perm.who_ug_name,
+					    sizeof (node->who_perm.who_ug_name),
+					    "(unknown: %d)", rid);
+				}
 			}
 
 			uu_avl_insert(avl, node, idx);
@@ -5773,9 +5780,9 @@ construct_fsacl_list(boolean_t un, struct allow_opts *opts, nvlist_t **nvlp)
 
 				if (p != NULL)
 					rid = p->pw_uid;
-				else {
+				else if (*endch != '\0') {
 					(void) snprintf(errbuf, 256, gettext(
-					    "invalid user %s"), curr);
+					    "invalid user %s\n"), curr);
 					allow_usage(un, B_TRUE, errbuf);
 				}
 			} else if (opts->group) {
@@ -5787,9 +5794,9 @@ construct_fsacl_list(boolean_t un, struct allow_opts *opts, nvlist_t **nvlp)
 
 				if (g != NULL)
 					rid = g->gr_gid;
-				else {
+				else if (*endch != '\0') {
 					(void) snprintf(errbuf, 256, gettext(
-					    "invalid group %s"),  curr);
+					    "invalid group %s\n"),  curr);
 					allow_usage(un, B_TRUE, errbuf);
 				}
 			} else {
@@ -5815,7 +5822,7 @@ construct_fsacl_list(boolean_t un, struct allow_opts *opts, nvlist_t **nvlp)
 					rid = g->gr_gid;
 				} else {
 					(void) snprintf(errbuf, 256, gettext(
-					    "invalid user/group %s"), curr);
+					    "invalid user/group %s\n"), curr);
 					allow_usage(un, B_TRUE, errbuf);
 				}
 			}