diff --git a/src/uniq.c b/src/uniq.c
index b3fd424..d8c0e7d 100644
--- a/src/uniq.c
+++ b/src/uniq.c
@@ -151,6 +151,11 @@ int main(int argc, char * argv[])
 			case 'u':
 				opts |= OPTS_u;
 				break;
+			case 'f':
+			case 's':
+				fprintf(stderr, "%s%c%s", "uniq: -", o,
+						": Not implemented yet\n");
+				return _usage();
 			default:
 				return _usage();
 		}