diff --git a/src/threads.c b/src/threads.c
index e90d3ff..815e623 100644
--- a/src/threads.c
+++ b/src/threads.c
@@ -29,6 +29,7 @@ void cleanPromise(struct Promise* promise)
 {
     promise->refs -= 1;
     if (promise->refs == 0) {
+        deleteEnv(promise->env);
         free(promise);
     }
 }
@@ -68,6 +69,7 @@ Object async(Object* params, int length, struct Environment* env)
         .env = env,
         .object = params[0], // TODO: Clone?
     };
+    env->refs += 1;
 
     pthread_create(&promise.promise->thread, NULL, doAsync, promise.promise);
     return promise;