diff --git a/ext/tox/tox.c b/ext/tox/tox.c
index 9f277d7..d93cc0e 100644
--- a/ext/tox/tox.c
+++ b/ext/tox/tox.c
@@ -54,7 +54,9 @@ VALUE cTox_initialize(const VALUE self, const VALUE options)
   cTox_ *tox;
   cTox_cOptions_ *tox_options;
 
-  /* check if `options` is instance of `Tox::Options` */
+  // check if `options` is instance of `Tox::Options`
+  if (Qfalse == rb_funcall(options, rb_intern("is_a?"), 1, cTox_cOptions))
+    rb_raise(rb_eTypeError, "argument 1 should be Tox::Options");
 
   Data_Get_Struct(self, cTox_, tox);
   Data_Get_Struct(options, cTox_cOptions_, tox_options);