diff --git a/block-sys/src/lib.rs b/block-sys/src/lib.rs
index b989303ea..9fb38f84d 100644
--- a/block-sys/src/lib.rs
+++ b/block-sys/src/lib.rs
@@ -35,7 +35,7 @@ pub struct Class {
     _priv: [u8; 0],
 
     /// See objc_sys::OpaqueData
-    _opaque: PhantomData<(UnsafeCell<()>, *const UnsafeCell<()>, PhantomPinned)>,
+    _opaque: UnsafeCell<PhantomData<(*const UnsafeCell<()>, PhantomPinned)>>,
 }
 
 /// Block descriptor flags.
diff --git a/objc-sys/src/lib.rs b/objc-sys/src/lib.rs
index 5e733ec5a..12f0f5add 100644
--- a/objc-sys/src/lib.rs
+++ b/objc-sys/src/lib.rs
@@ -130,7 +130,7 @@ pub use various::*;
 /// (It's also less of a breaking change on our part if we re-add these).
 ///
 /// TODO: Replace this with `extern type` to also mark it as `!Sized`.
-type OpaqueData = PhantomData<(UnsafeCell<()>, *const UnsafeCell<()>, PhantomPinned)>;
+type OpaqueData = UnsafeCell<PhantomData<(*const UnsafeCell<()>, PhantomPinned)>>;
 
 #[cfg(test)]
 mod tests {