diff --git a/lib/packer.ts b/lib/packer.ts
index fc6d589..3ea66b3 100644
--- a/lib/packer.ts
+++ b/lib/packer.ts
@@ -100,7 +100,6 @@ const pack_value = (e: E, value: unknown) => {
       ? Array.isArray(value) ? list(e, value) : map(e, value)
       : small_atom(e, [110, 105, 108]);
     case "string": return string(e, value);
-    case "undefined": return small_atom(e, [110, 105, 108]);
     default: throw new Error(`Unsupported type '${typeof value}'`);
   }
 };