diff --git a/src/test/run-pass/drop/dynamic-drop.rs b/src/test/run-pass/drop/dynamic-drop.rs
index 41814f2af16b4..7aa2b0efc7f25 100644
--- a/src/test/run-pass/drop/dynamic-drop.rs
+++ b/src/test/run-pass/drop/dynamic-drop.rs
@@ -10,6 +10,7 @@
 #![feature(slice_patterns)]
 
 use std::cell::{Cell, RefCell};
+use std::mem::ManuallyDrop;
 use std::ops::Generator;
 use std::panic;
 use std::usize;
@@ -139,17 +140,16 @@ fn assignment1(a: &Allocator, c0: bool) {
     _v = _w;
 }
 
-#[allow(unions_with_drop_fields)]
 union Boxy<T> {
-    a: T,
-    b: T,
+    a: ManuallyDrop<T>,
+    b: ManuallyDrop<T>,
 }
 
 fn union1(a: &Allocator) {
     unsafe {
-        let mut u = Boxy { a: a.alloc() };
-        u.b = a.alloc();
-        drop(u.a);
+        let mut u = Boxy { a: ManuallyDrop::new(a.alloc()) };
+        *u.b = a.alloc(); // drops first alloc
+        drop(ManuallyDrop::into_inner(u.a));
     }
 }
 
diff --git a/src/test/run-pass/self/self-in-typedefs.rs b/src/test/run-pass/self/self-in-typedefs.rs
index 9c0906013fafc..cd7a68ec06146 100644
--- a/src/test/run-pass/self/self-in-typedefs.rs
+++ b/src/test/run-pass/self/self-in-typedefs.rs
@@ -3,7 +3,8 @@
 #![feature(untagged_unions)]
 
 #![allow(dead_code)]
-#![allow(unions_with_drop_fields)]
+
+use std::mem::ManuallyDrop;
 
 enum A<'a, T: 'a>
 where
@@ -24,6 +25,14 @@ where
 union C<'a, T: 'a>
 where
     Self: Send, T: PartialEq<Self>
+{
+    foo: &'a Self,
+    bar: ManuallyDrop<T>,
+}
+
+union D<'a, T: 'a>
+where
+    Self: Send, T: PartialEq<Self> + Copy
 {
     foo: &'a Self,
     bar: T,