diff --git a/sexp.c b/sexp.c
index 6613672e..424df860 100644
--- a/sexp.c
+++ b/sexp.c
@@ -527,6 +527,7 @@ static const char* sexp_initial_features[] = {
   "ratios",
 #endif
   "r7rs",
+  "chibi-" sexp_version,
   "chibi",
   NULL,
 };