diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index c8d073e8..49330c8d 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -449,7 +449,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.22.1"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=ef2bd6d043d8675badaa415db89be7b52439725f#ef2bd6d043d8675badaa415db89be7b52439725f"
+source = "git+https://github.com/udesou/mmtk-core.git?rev=e9660c7ffca6a0d7fb5efb159482d89053f5d203#e9660c7ffca6a0d7fb5efb159482d89053f5d203"
 dependencies = [
  "atomic 0.6.0",
  "atomic-traits",
@@ -500,7 +500,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.22.1"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=ef2bd6d043d8675badaa415db89be7b52439725f#ef2bd6d043d8675badaa415db89be7b52439725f"
+source = "git+https://github.com/udesou/mmtk-core.git?rev=e9660c7ffca6a0d7fb5efb159482d89053f5d203#e9660c7ffca6a0d7fb5efb159482d89053f5d203"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index 8c514be9..8608c1be 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/udesou/julia.git"
-julia_version = "4792b73132850aa153fe22023b8a45af29a3554f"
+julia_version = "4e057c98921ee71c4b86553df039923857a72c8f"
 
 [lib]
 crate-type = ["cdylib"]
diff --git a/mmtk/api/mmtk.h b/mmtk/api/mmtk.h
index e3d10c4a..9ddd411b 100644
--- a/mmtk/api/mmtk.h
+++ b/mmtk/api/mmtk.h
@@ -95,8 +95,6 @@ extern bool mmtk_process(char* name, char* value);
 extern void mmtk_scan_region(void);
 extern void mmtk_handle_user_collection_request(void *tls, uint8_t collection);
 extern void mmtk_initialize_collection(void* tls);
-extern void mmtk_enable_collection(void);
-extern void mmtk_disable_collection(void);
 extern void mmtk_start_control_collector(void *tls);
 extern void mmtk_start_worker(void *tls, void* worker, void* mmtk);
 extern void mmtk_process_julia_obj(void* addr);
diff --git a/mmtk/src/api.rs b/mmtk/src/api.rs
index 5bdfd7e6..a8eaa11a 100644
--- a/mmtk/src/api.rs
+++ b/mmtk/src/api.rs
@@ -3,7 +3,6 @@
 
 use crate::JuliaVM;
 use crate::Julia_Upcalls;
-use crate::BLOCK_FOR_GC;
 use crate::JULIA_HEADER_SIZE;
 use crate::SINGLETON;
 use crate::UPCALLS;
diff --git a/mmtk/src/collection.rs b/mmtk/src/collection.rs
index 92e157c8..c648fe90 100644
--- a/mmtk/src/collection.rs
+++ b/mmtk/src/collection.rs
@@ -5,7 +5,7 @@ use mmtk::util::alloc::AllocationError;
 use mmtk::util::opaque_pointer::*;
 use mmtk::vm::{Collection, GCThreadContext};
 use mmtk::Mutator;
-use std::sync::atomic::{AtomicBool, AtomicIsize, AtomicU64, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicIsize, AtomicU32, AtomicU64, Ordering};
 
 use crate::{BLOCK_FOR_GC, STW_COND, WORLD_HAS_STOPPED};