diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index 3767571..e1a285e 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -122,17 +122,18 @@ checksum = "4da9a32f3fed317401fa3c862968128267c3106685286e15d5aaa3d7389c2f60"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.59",
+ "syn 2.0.60",
 ]
 
 [[package]]
 name = "cc"
-version = "1.0.94"
+version = "1.0.95"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "17f6e324229dc011159fcc089755d1e2e216a90d43a7dea6853ca740b84f35e7"
+checksum = "d32a725bc159af97c3e629873bb9f88fb8cf8a4867175f76dc987815ea07c83b"
 dependencies = [
  "jobserver",
  "libc",
+ "once_cell",
 ]
 
 [[package]]
@@ -217,7 +218,7 @@ checksum = "4e018fccbeeb50ff26562ece792ed06659b9c2dae79ece77c4456bb10d9bf79b"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.59",
+ "syn 2.0.60",
 ]
 
 [[package]]
@@ -249,7 +250,7 @@ checksum = "f282cfdfe92516eb26c2af8589c274c7c17681f5ecc03c18255fe741c6aa64eb"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.59",
+ "syn 2.0.60",
 ]
 
 [[package]]
@@ -347,9 +348,9 @@ dependencies = [
 
 [[package]]
 name = "jobserver"
-version = "0.1.30"
+version = "0.1.31"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "685a7d121ee3f65ae4fddd72b25a04bb36b6af81bc0828f7d5434c0fe60fa3a2"
+checksum = "d2b099aaa34a9751c5bf0878add70444e1ed2dd73f347be99003d4577277de6e"
 dependencies = [
  "libc",
 ]
@@ -424,7 +425,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.24.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=e79e94e744660c486d5471f252ff05c4248bcea9#e79e94e744660c486d5471f252ff05c4248bcea9"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=a02803b4104519ff2289234101a2dd8ceedd1bc7#a02803b4104519ff2289234101a2dd8ceedd1bc7"
 dependencies = [
  "atomic",
  "atomic-traits",
@@ -459,12 +460,12 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.24.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=e79e94e744660c486d5471f252ff05c4248bcea9#e79e94e744660c486d5471f252ff05c4248bcea9"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=a02803b4104519ff2289234101a2dd8ceedd1bc7#a02803b4104519ff2289234101a2dd8ceedd1bc7"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
  "quote",
- "syn 2.0.59",
+ "syn 2.0.60",
 ]
 
 [[package]]
@@ -684,7 +685,7 @@ dependencies = [
  "proc-macro2",
  "quote",
  "rustversion",
- "syn 2.0.59",
+ "syn 2.0.60",
 ]
 
 [[package]]
@@ -699,9 +700,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.59"
+version = "2.0.60"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4a6531ffc7b071655e4ce2e04bd464c4830bb585a61cabb96cf808f05172615a"
+checksum = "909518bc7b1c9b779f1bbf07f2929d35af9f0f37e47c6e9ef7f9dddc1e1821f3"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -710,9 +711,9 @@ dependencies = [
 
 [[package]]
 name = "sysinfo"
-version = "0.30.10"
+version = "0.30.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "26d7c217777061d5a2d652aea771fb9ba98b6dade657204b08c4b9604d11555b"
+checksum = "87341a165d73787554941cd5ef55ad728011566fe714e987d1b976c15dbc3a83"
 dependencies = [
  "cfg-if",
  "core-foundation-sys",
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index d049c9a..face613 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -27,7 +27,7 @@ log = "*"
 # - 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 = "e79e94e744660c486d5471f252ff05c4248bcea9" }
+mmtk = { git = "https://github.com/mmtk/mmtk-core.git", rev = "a02803b4104519ff2289234101a2dd8ceedd1bc7" }
 # Uncomment the following and fix the path to mmtk-core to build locally
 # mmtk = { path = "../repos/mmtk-core" }
 
diff --git a/mmtk/src/object_model.rs b/mmtk/src/object_model.rs
index 4735fcf..dda1026 100644
--- a/mmtk/src/object_model.rs
+++ b/mmtk/src/object_model.rs
@@ -69,7 +69,8 @@ impl ObjectModel<V8> for VMObjectModel {
     }
 
     fn address_to_ref(address: Address) -> ObjectReference {
-        ObjectReference::from_raw_address(address)
+        debug_assert!(!address.is_zero());
+        unsafe { ObjectReference::from_raw_address_unchecked(address) }
     }
 
     fn dump_object(object: ObjectReference) {
diff --git a/mmtk/src/reference_glue.rs b/mmtk/src/reference_glue.rs
index bd58d0f..ea2684c 100644
--- a/mmtk/src/reference_glue.rs
+++ b/mmtk/src/reference_glue.rs
@@ -11,10 +11,13 @@ impl ReferenceGlue<V8> for VMReferenceGlue {
     fn set_referent(_reff: ObjectReference, _referent: ObjectReference) {
         unimplemented!()
     }
-    fn get_referent(_object: ObjectReference) -> ObjectReference {
+    fn get_referent(_object: ObjectReference) -> Option<ObjectReference> {
         unimplemented!()
     }
     fn enqueue_references(_references: &[ObjectReference], _tls: VMWorkerThread) {
         unimplemented!()
     }
+    fn clear_referent(_new_reference: ObjectReference) {
+        unimplemented!()
+    }
 }