diff --git a/src/fir2csv/999_main.c b/src/fir2csv/999_main.c
index e47f7cb..44a796b 100644
--- a/src/fir2csv/999_main.c
+++ b/src/fir2csv/999_main.c
@@ -32,7 +32,7 @@ const struct option options[] = {
     { 0, 0, 0, 0 }
 };
 
-const char* optstr = "hn:o:V";
+const char* optstr = "hn:o:tV";