diff --git a/tests/ui/async-await/async-drop.rs b/tests/ui/async-await/async-drop.rs
index 12f120a0b1216..4e60598661faf 100644
--- a/tests/ui/async-await/async-drop.rs
+++ b/tests/ui/async-await/async-drop.rs
@@ -53,18 +53,20 @@ fn main() {
     let i = 13;
     let fut = pin!(async {
         test_async_drop(Int(0), 0).await;
-        test_async_drop(AsyncInt(0), 104).await;
-        test_async_drop([AsyncInt(1), AsyncInt(2)], 152).await;
-        test_async_drop((AsyncInt(3), AsyncInt(4)), 488).await;
+        // FIXME(#63818): niches in coroutines are disabled.
+        // Some of these sizes should be smaller, as indicated in comments.
+        test_async_drop(AsyncInt(0), /*104*/ 112).await;
+        test_async_drop([AsyncInt(1), AsyncInt(2)], /*152*/ 168).await;
+        test_async_drop((AsyncInt(3), AsyncInt(4)), /*488*/ 528).await;
         test_async_drop(5, 0).await;
         let j = 42;
         test_async_drop(&i, 0).await;
         test_async_drop(&j, 0).await;
-        test_async_drop(AsyncStruct { b: AsyncInt(8), a: AsyncInt(7), i: 6 }, 1688).await;
+        test_async_drop(AsyncStruct { b: AsyncInt(8), a: AsyncInt(7), i: 6 }, /*1688*/ 1792).await;
         test_async_drop(ManuallyDrop::new(AsyncInt(9)), 0).await;
 
         let foo = AsyncInt(10);
-        test_async_drop(AsyncReference { foo: &foo }, 104).await;
+        test_async_drop(AsyncReference { foo: &foo }, /*104*/ 112).await;
 
         let foo = AsyncInt(11);
         test_async_drop(
@@ -73,17 +75,17 @@ fn main() {
                 let foo = AsyncInt(10);
                 foo
             },
-            120,
+            /*120*/ 136,
         )
         .await;
 
-        test_async_drop(AsyncEnum::A(AsyncInt(12)), 680).await;
-        test_async_drop(AsyncEnum::B(SyncInt(13)), 680).await;
+        test_async_drop(AsyncEnum::A(AsyncInt(12)), /*680*/ 736).await;
+        test_async_drop(AsyncEnum::B(SyncInt(13)), /*680*/ 736).await;
 
-        test_async_drop(SyncInt(14), 16).await;
+        test_async_drop(SyncInt(14), /*16*/ 24).await;
         test_async_drop(
             SyncThenAsync { i: 15, a: AsyncInt(16), b: SyncInt(17), c: AsyncInt(18) },
-            3064,
+            /*3064*/ 3296,
         )
         .await;
 
@@ -99,11 +101,11 @@ fn main() {
                 black_box(core::future::ready(())).await;
                 foo
             },
-            120,
+            /*120*/ 136,
         )
         .await;
 
-        test_async_drop(AsyncUnion { signed: 21 }, 32).await;
+        test_async_drop(AsyncUnion { signed: 21 }, /*32*/ 40).await;
     });
     let res = fut.poll(&mut cx);
     assert_eq!(res, Poll::Ready(()));
diff --git a/tests/ui/async-await/future-sizes/async-awaiting-fut.stdout b/tests/ui/async-await/future-sizes/async-awaiting-fut.stdout
index def967ba195ef..642e27b2a57d6 100644
--- a/tests/ui/async-await/future-sizes/async-awaiting-fut.stdout
+++ b/tests/ui/async-await/future-sizes/async-awaiting-fut.stdout
@@ -14,28 +14,26 @@ print-type-size         field `.value`: 3077 bytes
 print-type-size type: `{async fn body of calls_fut<{async fn body of big_fut()}>()}`: 3077 bytes, alignment: 1 bytes
 print-type-size     discriminant: 1 bytes
 print-type-size     variant `Unresumed`: 1025 bytes
-print-type-size         upvar `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
+print-type-size         upvar `.fut`: 1025 bytes
 print-type-size     variant `Suspend0`: 2052 bytes
-print-type-size         upvar `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
-print-type-size         padding: 1 bytes
-print-type-size         local `.fut`: 1025 bytes, alignment: 1 bytes
+print-type-size         upvar `.fut`: 1025 bytes
+print-type-size         local `.fut`: 1025 bytes
 print-type-size         local `..coroutine_field4`: 1 bytes, type: bool
 print-type-size         local `.__awaitee`: 1 bytes, type: {async fn body of wait()}
 print-type-size     variant `Suspend1`: 3076 bytes
-print-type-size         upvar `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
-print-type-size         padding: 1026 bytes
+print-type-size         upvar `.fut`: 1025 bytes
+print-type-size         padding: 1025 bytes
 print-type-size         local `..coroutine_field4`: 1 bytes, alignment: 1 bytes, type: bool
 print-type-size         local `.__awaitee`: 1025 bytes, type: {async fn body of big_fut()}
 print-type-size     variant `Suspend2`: 2052 bytes
-print-type-size         upvar `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
-print-type-size         padding: 1 bytes
-print-type-size         local `.fut`: 1025 bytes, alignment: 1 bytes
+print-type-size         upvar `.fut`: 1025 bytes
+print-type-size         local `.fut`: 1025 bytes
 print-type-size         local `..coroutine_field4`: 1 bytes, type: bool
 print-type-size         local `.__awaitee`: 1 bytes, type: {async fn body of wait()}
 print-type-size     variant `Returned`: 1025 bytes
-print-type-size         upvar `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
+print-type-size         upvar `.fut`: 1025 bytes
 print-type-size     variant `Panicked`: 1025 bytes
-print-type-size         upvar `.fut`: 1025 bytes, offset: 0 bytes, alignment: 1 bytes
+print-type-size         upvar `.fut`: 1025 bytes
 print-type-size type: `std::mem::ManuallyDrop<{async fn body of big_fut()}>`: 1025 bytes, alignment: 1 bytes
 print-type-size     field `.value`: 1025 bytes
 print-type-size type: `std::mem::MaybeUninit<{async fn body of big_fut()}>`: 1025 bytes, alignment: 1 bytes
diff --git a/tests/ui/coroutine/discriminant.rs b/tests/ui/coroutine/discriminant.rs
index d6879e2182556..ca4fcedd7e536 100644
--- a/tests/ui/coroutine/discriminant.rs
+++ b/tests/ui/coroutine/discriminant.rs
@@ -124,12 +124,14 @@ fn main() {
     };
 
     assert_eq!(size_of_val(&gen_u8_tiny_niche()), 1);
-    assert_eq!(size_of_val(&Some(gen_u8_tiny_niche())), 1); // uses niche
+    // FIXME(#63818): niches in coroutines are disabled.
+    // assert_eq!(size_of_val(&Some(gen_u8_tiny_niche())), 1); // uses niche
     assert_eq!(size_of_val(&Some(Some(gen_u8_tiny_niche()))), 2); // cannot use niche anymore
     assert_eq!(size_of_val(&gen_u8_full()), 1);
     assert_eq!(size_of_val(&Some(gen_u8_full())), 2); // cannot use niche
     assert_eq!(size_of_val(&gen_u16()), 2);
-    assert_eq!(size_of_val(&Some(gen_u16())), 2); // uses niche
+    // FIXME(#63818): niches in coroutines are disabled.
+    // assert_eq!(size_of_val(&Some(gen_u16())), 2); // uses niche
 
     cycle(gen_u8_tiny_niche(), 254);
     cycle(gen_u8_full(), 255);
diff --git a/tests/ui/coroutine/niche-in-coroutine.rs b/tests/ui/coroutine/niche-in-coroutine.rs
index 117ee9e6f0386..f268ef09f8923 100644
--- a/tests/ui/coroutine/niche-in-coroutine.rs
+++ b/tests/ui/coroutine/niche-in-coroutine.rs
@@ -15,5 +15,6 @@ fn main() {
         take(x);
     };
 
-    assert_eq!(size_of_val(&gen1), size_of_val(&Some(gen1)));
+    // FIXME(#63818): niches in coroutines are disabled. Should be `assert_eq`.
+    assert_ne!(size_of_val(&gen1), size_of_val(&Some(gen1)));
 }