diff --git a/implementations/C/joy b/implementations/C/joy
index 424aade..a32fd77 100755
Binary files a/implementations/C/joy and b/implementations/C/joy differ
diff --git a/implementations/C/joy.c b/implementations/C/joy.c
index 25664fa..ba0cc30 100644
--- a/implementations/C/joy.c
+++ b/implementations/C/joy.c
@@ -33,6 +33,13 @@ void* reallocate_function (void *ptr, size_t old_size, size_t new_size) {
 void deallocate_function (void *ptr, size_t size) {
     GC_free(ptr);
 }
+
+void my_callback(GC_PTR void_obj, GC_PTR void_environment) {
+    //MY_ENVIRONMENT *env = (MY_ENVIRONMENT)void_environment;
+    mpz_t *obj = (mpz_t*)void_obj;
+    mpz_clear(*obj);
+}
+
 int main(void)
 {
     mp_set_memory_functions(
@@ -40,7 +47,13 @@ int main(void)
         &reallocate_function,
         &deallocate_function
         );
+    mpz_t pie;
+    //mpz_init_set_str (pie, "3141592653589793238462643383279502884", 10);
+    mpz_init_set_str (pie, "25d0c79fe247f31777d922627a74624", 16);
+    gmp_printf ("%Zd = %Zx\n", pie, pie);
+    GC_register_finalizer(pie, my_callback, NULL, NULL, NULL);
     return 0;
+
     //return to_i(car(cons(from_i(0),from_i(1))));
 }