diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index 6f0573af..893d36a0 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -534,7 +534,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.18.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=638d3287023c77fb4b6906a8bab35a77a5fb6a1f#638d3287023c77fb4b6906a8bab35a77a5fb6a1f"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=2cc34abe2b3ce4ee213b9ac4b9295160dac754cc#2cc34abe2b3ce4ee213b9ac4b9295160dac754cc"
 dependencies = [
  "atomic 0.5.1",
  "atomic-traits",
@@ -578,7 +578,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.18.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=638d3287023c77fb4b6906a8bab35a77a5fb6a1f#638d3287023c77fb4b6906a8bab35a77a5fb6a1f"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=2cc34abe2b3ce4ee213b9ac4b9295160dac754cc#2cc34abe2b3ce4ee213b9ac4b9295160dac754cc"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index 8a4aa638..e3d3705c 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -10,7 +10,7 @@ edition = "2018"
 [package.metadata.julia]
 # Our CI matches the following line and extract mmtk/julia. If this line is updated, please check ci yaml files and make sure it works.
 julia_repo = "https://github.com/mmtk/julia.git"
-julia_version = "9dbc8fc65e1e273cefbbe87b20e35e4c43a7ebaf"
+julia_version = "a760a7ee28150261669cb0b31a8284214b3635c7"
 
 [lib]
 crate-type = ["staticlib", "rlib", "dylib"]
@@ -29,7 +29,7 @@ lazy_static = "1.1"
 # - 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 = "638d3287023c77fb4b6906a8bab35a77a5fb6a1f" }
+mmtk = { git = "https://github.com/mmtk/mmtk-core.git", rev = "2cc34abe2b3ce4ee213b9ac4b9295160dac754cc" }
 # Uncomment the following to build locally
 # mmtk = { path = "../repos/mmtk-core" }
 log = {version = "0.4", features = ["max_level_trace", "release_max_level_off"] }
diff --git a/mmtk/api/mmtk.h b/mmtk/api/mmtk.h
index caf1c402..2841f0a2 100644
--- a/mmtk/api/mmtk.h
+++ b/mmtk/api/mmtk.h
@@ -57,7 +57,8 @@ extern void modify_check(void* ref);
 extern int object_is_managed_by_mmtk(void* addr);
 extern void runtime_panic(void);
 
-
+extern void mmtk_object_reference_write_post(MMTk_Mutator mutator, const void* src, const void* target);
+extern uint8_t mmtk_needs_write_barrier(void);
 
 /**
  * Tracing
diff --git a/mmtk/src/api.rs b/mmtk/src/api.rs
index 2e0df1a1..e54339b2 100644
--- a/mmtk/src/api.rs
+++ b/mmtk/src/api.rs
@@ -447,3 +447,29 @@ pub extern "C" fn mmtk_gc_poll(tls: VMMutatorThread) {
 pub extern "C" fn runtime_panic() {
     panic!("Panicking at runtime!")
 }
+
+#[no_mangle]
+pub extern "C" fn mmtk_object_reference_write_post(
+    mutator: *mut Mutator<JuliaVM>,
+    src: ObjectReference,
+    target: ObjectReference,
+) {
+    let mutator = unsafe { &mut *mutator };
+    memory_manager::object_reference_write_post(
+        mutator,
+        src,
+        crate::edges::JuliaVMEdge::Simple(mmtk::vm::edge_shape::SimpleEdge::from_address(
+            Address::ZERO,
+        )),
+        target,
+    )
+}
+
+#[no_mangle]
+pub extern "C" fn mmtk_needs_write_barrier() -> u8 {
+    use mmtk::plan::BarrierSelector;
+    match SINGLETON.get_plan().constraints().barrier {
+        BarrierSelector::NoBarrier => 0,
+        BarrierSelector::ObjectBarrier => 1,
+    }
+}