diff --git a/Cargo.toml b/Cargo.toml
index a6c95cc..85fadee 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "v9"
-version = "0.1.42"
+version = "0.1.43"
 authors = ["neptunepink <purpleposeidon@gmail.com>"]
 edition = "2018"
 license = "MIT/Apache-2.0"
diff --git a/src/id.rs b/src/id.rs
index d4f1ccf..1eb18a7 100644
--- a/src/id.rs
+++ b/src/id.rs
@@ -11,7 +11,14 @@ use std::cmp::Ordering;
 
 type Run<M> = (Id<M>, Id<M>);
 
-pub trait Raw: 'static + Copy + fmt::Debug + Ord + Send + Sync + hash::Hash + serde::Serialize + serde::de::DeserializeOwned + Add<Output=Self> + Sub<Output=Self> {
+pub trait Raw
+where
+    Self: 'static + Send + Sync,
+    Self: Ord + Copy + fmt::Debug + hash::Hash,
+    Self: serde::Serialize + serde::de::DeserializeOwned,
+    Self: Add<Output=Self> + Sub<Output=Self>,
+    Self: self::raw_impl::Sealed,
+{
     fn to_usize(self) -> usize;
     fn from_usize(x: usize) -> Self;
     fn offset(self, d: i8) -> Self;
@@ -19,9 +26,12 @@ pub trait Raw: 'static + Copy + fmt::Debug + Ord + Send + Sync + hash::Hash + se
     const LAST: Self;
 }
 mod raw_impl {
+    /// Forbid non-primitives from being put into a SyncRef.
+    pub trait Sealed {}
     use super::Raw;
     macro_rules! imp {
         ($($ty:ident),*) => {$(
+            impl Sealed for $ty {}
             impl Raw for $ty {
                 #[inline]
                 fn to_usize(self) -> usize { self as usize }
diff --git a/src/util.rs b/src/util.rs
index 99500b4..b368395 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -1,32 +1,47 @@
 use std::cell::RefCell;
 use std::ops::Deref;
+use crate::prelude_lib::RunList;
+use crate::table::TableMarker;
 
 /// A `Sync`able `RefCell`.
 #[derive(Default, Debug, Clone)]
 pub struct SyncRef<T> {
     val: RefCell<T>,
 }
-impl<T> SyncRef<T> {
-    pub fn new(val: T) -> Self {
+impl<T: TableMarker> SyncRef<RunList<T>> {
+    pub fn new(val: RunList<T>) -> Self {
         SyncRef {
             val: RefCell::new(val),
         }
     }
-    pub fn get_mut(&mut self) -> &mut T {
+    pub fn get_mut(&mut self) -> &mut RunList<T> {
         self.val.get_mut()
     }
-    pub fn as_cell(&mut self) -> &RefCell<T> {
+    pub fn as_cell(&mut self) -> &RefCell<RunList<T>> {
         &self.val
     }
-    pub unsafe fn as_cell_unsafe(&self) -> &RefCell<T> {
+    pub unsafe fn as_cell_unsafe(&self) -> &RefCell<RunList<T>> {
         &self.val
     }
 }
 // Trying to impl Deref/DerefMut provokes odd curiosities.
-unsafe impl<T: Send> Send for SyncRef<T> {}
-unsafe impl<T> Sync for SyncRef<T> {}
+unsafe impl<T: TableMarker> Send for SyncRef<RunList<T>> {}
+unsafe impl<T: TableMarker> Sync for SyncRef<RunList<T>> {}
 // FIXME: Ugh, this is probably unsound.
 
+/// ```compile_fail
+/// use std::cell::Cell;
+/// use v9::util::SyncRef;
+///
+/// fn main() {
+///     let sync_ref = SyncRef::new(Cell::new(0));
+///     fn check<T: Send + Sync>(_: T) {}
+///     check(sync_ref);
+/// }
+/// ```
+#[cfg(doctest)]
+struct SyncRefSyncless;
+
 /// A `&mut T` that pretends it's a `&T`.
 pub struct MutButRef<'a, T>(&'a mut T);
 impl<'a, T> MutButRef<'a, T> {