diff --git a/tools/sexp-conv.c b/tools/sexp-conv.c
index 75b7ab250eb59552847e9b0f51096dafea6f0bd0..9443f4be89c77c41301316fdc8ed4d79a2c676a0 100644
--- a/tools/sexp-conv.c
+++ b/tools/sexp-conv.c
@@ -1016,6 +1016,7 @@ parse_options(struct conv_options *o,
 	      int argc, char **argv)
 {  
   o->mode = SEXP_ADVANCED;
+  o->prefer_hex = 0;
   o->once = 0;
   o->hash = NULL;
   o->width = 72;