diff --git a/lib/chibi/ast.c b/lib/chibi/ast.c
index 7d557edf..551e5aa2 100644
--- a/lib/chibi/ast.c
+++ b/lib/chibi/ast.c
@@ -181,6 +181,11 @@ static sexp sexp_type_of (sexp ctx, sexp self, sexp_sint_t n, sexp x) {
     return sexp_type_by_index(ctx, SEXP_OBJECT);
 }
 
+static sexp sexp_env_parent_op (sexp ctx, sexp self, sexp_sint_t n, sexp e) {
+  sexp_assert_type(ctx, sexp_envp, SEXP_ENV, e);
+  return sexp_env_parent(e) ? sexp_env_parent(e) : SEXP_FALSE;
+}
+
 static sexp sexp_type_name_op (sexp ctx, sexp self, sexp_sint_t n, sexp t) {
   sexp_assert_type(ctx, sexp_typep, SEXP_TYPE, t);
   return sexp_type_name(t);
@@ -450,6 +455,7 @@ sexp sexp_init_library (sexp ctx, sexp self, sexp_sint_t n, sexp env, const char
   sexp_define_foreign(ctx, env, "type-slots", 1, sexp_type_slots_op);
   sexp_define_foreign(ctx, env, "type-num-slots", 1, sexp_type_num_slots_op);
   sexp_define_foreign(ctx, env, "type-printer", 1, sexp_type_printer_op);
+  sexp_define_foreign(ctx, env, "environment-parent", 1, sexp_env_parent_op);
   sexp_define_foreign(ctx, env, "object-size", 1, sexp_object_size);
   sexp_define_foreign_opt(ctx, env, "integer->immediate", 2, sexp_integer_to_immediate, SEXP_FALSE);
   sexp_define_foreign(ctx, env, "gc", 0, sexp_gc_op);
diff --git a/lib/chibi/ast.sld b/lib/chibi/ast.sld
index df486f42..74b90c16 100644
--- a/lib/chibi/ast.sld
+++ b/lib/chibi/ast.sld
@@ -30,6 +30,7 @@
    bytecode-name bytecode-literals bytecode-source
    pair-source pair-source-set!
    port-line port-line-set!
+   environment-parent
    type-name type-cpl type-parent type-slots type-num-slots type-printer
    object-size integer->immediate gc
    string-contains integer->error-string