Fix MostlyAdequate#264

tama8947 · Dec 1, 2018 · 15f8af5 · 15f8af5
1 parent 45f7160
commit 15f8af5
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/appendix_b.md b/appendix_b.md
@@ -234,7 +234,9 @@ class IO {
   }
 
   join() {
-    return this.unsafePerformIO();
+    return new IO(() => {
+      return this.unsafePerformIO().unsafePerformIO();
+    });
   }
 }
 ```