diff --git a/bwtsw2_main.c b/bwtsw2_main.c
index afbad2eb..02560e58 100644
--- a/bwtsw2_main.c
+++ b/bwtsw2_main.c
@@ -34,6 +34,7 @@ int bwa_bwtsw2(int argc, char *argv[])
 		case 'N': opt->t_seeds = atoi(optarg); break;
 		case 'H': opt->hard_clip = 1; break;
 		case 'f': xreopen(optarg, "w", stdout); break;
+		default: return 1;
 		}
 	}
 	opt->qr = opt->q + opt->r;
diff --git a/simple_dp.c b/simple_dp.c
index 4cddb0b4..69ca8eaf 100644
--- a/simple_dp.c
+++ b/simple_dp.c
@@ -138,6 +138,7 @@ int bwa_stdsw(int argc, char *argv[])
 		case 'f': g_strand |= 1; break;
 		case 'r': g_strand |= 2; break;
 		case 'p': g_aa = 1; break;
+		default: return 1;
 		}
 	}
 	if (g_strand == 0) g_strand = 3;