diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index aad3f357..2d244423 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -438,7 +438,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.30.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=c0f97884234b51b13c8ba5d1563a8e0f592d11c2#c0f97884234b51b13c8ba5d1563a8e0f592d11c2"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=ec745353a8de72b645613e0fef3ab7f5f1ad9bd1#ec745353a8de72b645613e0fef3ab7f5f1ad9bd1"
 dependencies = [
  "atomic",
  "atomic-traits",
@@ -474,7 +474,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.30.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=c0f97884234b51b13c8ba5d1563a8e0f592d11c2#c0f97884234b51b13c8ba5d1563a8e0f592d11c2"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=ec745353a8de72b645613e0fef3ab7f5f1ad9bd1#ec745353a8de72b645613e0fef3ab7f5f1ad9bd1"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index c3808816..aaba99ed 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -35,7 +35,7 @@ probe = "0.5"
 # - change branch
 # - change repo name
 # But other changes including adding/removing whitespaces in commented lines may break the CI.
-mmtk = { git = "https://github.com/mmtk/mmtk-core.git", rev = "c0f97884234b51b13c8ba5d1563a8e0f592d11c2" }
+mmtk = { git = "https://github.com/mmtk/mmtk-core.git", rev = "ec745353a8de72b645613e0fef3ab7f5f1ad9bd1" }
 # Uncomment the following to build locally
 # mmtk = { path = "../repos/mmtk-core" }
 
@@ -72,3 +72,4 @@ pageprotect = []
 immix = []
 genimmix = []
 stickyimmix = []
+markcompact = []
diff --git a/mmtk/rust-toolchain b/mmtk/rust-toolchain
index 79e15fd4..6b4de0a4 100644
--- a/mmtk/rust-toolchain
+++ b/mmtk/rust-toolchain
@@ -1 +1 @@
-1.77.0
+1.83.0
diff --git a/mmtk/src/abi.rs b/mmtk/src/abi.rs
index 1ff7bef9..c950f305 100644
--- a/mmtk/src/abi.rs
+++ b/mmtk/src/abi.rs
@@ -329,7 +329,9 @@ impl OopDesc {
 
 impl fmt::Debug for OopDesc {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let c_string = unsafe { ((*UPCALLS).dump_object_string)(mem::transmute(self)) };
+        let c_string = unsafe {
+            ((*UPCALLS).dump_object_string)(mem::transmute::<&OopDesc, ObjectReference>(self))
+        };
         let c_str: &CStr = unsafe { CStr::from_ptr(c_string) };
         let s: &str = c_str.to_str().unwrap();
         write!(f, "{}", s)
diff --git a/mmtk/src/active_plan.rs b/mmtk/src/active_plan.rs
index 72022ffc..1406ef5d 100644
--- a/mmtk/src/active_plan.rs
+++ b/mmtk/src/active_plan.rs
@@ -12,7 +12,7 @@ struct OpenJDKMutatorIterator<'a, const COMPRESSED: bool> {
     phantom_data: PhantomData<&'a ()>,
 }
 
-impl<'a, const COMPRESSED: bool> OpenJDKMutatorIterator<'a, COMPRESSED> {
+impl<const COMPRESSED: bool> OpenJDKMutatorIterator<'_, COMPRESSED> {
     fn new() -> Self {
         let mut mutators = VecDeque::new();
         unsafe {
diff --git a/mmtk/src/api.rs b/mmtk/src/api.rs
index 4e619e2b..19c59580 100644
--- a/mmtk/src/api.rs
+++ b/mmtk/src/api.rs
@@ -235,12 +235,6 @@ pub extern "C" fn total_bytes() -> usize {
     with_singleton!(|singleton| memory_manager::total_bytes(singleton))
 }
 
-#[no_mangle]
-#[cfg(feature = "sanity")]
-pub extern "C" fn scan_region() {
-    with_singleton!(|singleton| memory_manager::scan_region(singleton))
-}
-
 #[no_mangle]
 pub extern "C" fn handle_user_collection_request(tls: VMMutatorThread) {
     with_singleton!(|singleton| {
diff --git a/mmtk/src/object_scanning.rs b/mmtk/src/object_scanning.rs
index 56dbda6c..c3143c8b 100644
--- a/mmtk/src/object_scanning.rs
+++ b/mmtk/src/object_scanning.rs
@@ -170,10 +170,10 @@ fn oop_iterate_slow<const COMPRESSED: bool, V: SlotVisitor<S<COMPRESSED>>>(
     unsafe {
         CLOSURE.with(|x| *x.get() = closure as *mut V as *mut u8);
         ((*UPCALLS).scan_object)(
-            mem::transmute(
+            mem::transmute::<*const unsafe extern "C" fn(Address), *mut libc::c_void>(
                 scan_object_fn::<COMPRESSED, V> as *const unsafe extern "C" fn(slot: Address),
             ),
-            mem::transmute(oop),
+            mem::transmute::<&OopDesc, ObjectReference>(oop),
             tls,
         );
     }
@@ -235,5 +235,7 @@ pub fn scan_object<const COMPRESSED: bool>(
     closure: &mut impl SlotVisitor<S<COMPRESSED>>,
     _tls: VMWorkerThread,
 ) {
-    unsafe { oop_iterate::<COMPRESSED>(mem::transmute(object), closure) }
+    unsafe {
+        oop_iterate::<COMPRESSED>(mem::transmute::<ObjectReference, &OopDesc>(object), closure)
+    }
 }