diff --git a/lib/chibi/ast.c b/lib/chibi/ast.c
index 1ebc16d8..7d557edf 100644
--- a/lib/chibi/ast.c
+++ b/lib/chibi/ast.c
@@ -358,6 +358,8 @@ sexp sexp_init_library (sexp ctx, sexp self, sexp_sint_t n, sexp env, const char
   sexp_define_type(ctx, "Byte-Vector", SEXP_BYTES);
   sexp_define_type(ctx, "Pair", SEXP_PAIR);
   sexp_define_type(ctx, "Vector", SEXP_VECTOR);
+  sexp_define_type(ctx, "Input-Port", SEXP_IPORT);
+  sexp_define_type(ctx, "Output-Port", SEXP_OPORT);
   sexp_define_type(ctx, "Opcode", SEXP_OPCODE);
   sexp_define_type(ctx, "Procedure", SEXP_PROCEDURE);
   sexp_define_type(ctx, "Bytecode", SEXP_BYTECODE);
diff --git a/lib/chibi/ast.sld b/lib/chibi/ast.sld
index 4222adb1..df486f42 100644
--- a/lib/chibi/ast.sld
+++ b/lib/chibi/ast.sld
@@ -2,7 +2,7 @@
 (define-library (chibi ast)
   (export
    analyze optimize env-cell ast->sexp macroexpand type-of
-   Object Opcode Procedure Bytecode Macro Env
+   Object Input-Port Output-Port Opcode Procedure Bytecode Macro Env
    Number Bignum Flonum Integer Char Boolean
    Symbol String Byte-Vector Vector Pair
    Context Lam Cnd Set Ref Seq Lit Sc Exception