Add missing C: to optstring
diff --git a/mkzftree.c b/mkzftree.c
index 8adfdb7..34ba132 100644
--- a/mkzftree.c
+++ b/mkzftree.c
@@ -94,7 +94,7 @@
 const char *program;
 
 /* Long options */
-#define OPTSTRING "fz:up:xXlLFvqV:hw"
+#define OPTSTRING "fz:up:xXC:lLFvqV:hw"
 #ifdef HAVE_GETOPT_LONG
 const struct option long_options[] = {
   { "force",	             0,  0,  'f' },