diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index 65492a30..0ecadfdf 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -545,7 +545,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.18.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=f1a0bb7fbec97dd84e35a40e8be01cf5018f2f9e#f1a0bb7fbec97dd84e35a40e8be01cf5018f2f9e"
+source = "git+https://github.com/qinsoon/mmtk-core.git?rev=cc405182954c24d3bd2d9cb61f4131080a7ccd4a#cc405182954c24d3bd2d9cb61f4131080a7ccd4a"
 dependencies = [
  "atomic 0.5.1",
  "atomic-traits",
@@ -570,6 +570,7 @@ dependencies = [
  "strum",
  "strum_macros",
  "sysinfo",
+ "variant_count",
 ]
 
 [[package]]
@@ -590,7 +591,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.18.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=f1a0bb7fbec97dd84e35a40e8be01cf5018f2f9e#f1a0bb7fbec97dd84e35a40e8be01cf5018f2f9e"
+source = "git+https://github.com/qinsoon/mmtk-core.git?rev=cc405182954c24d3bd2d9cb61f4131080a7ccd4a#cc405182954c24d3bd2d9cb61f4131080a7ccd4a"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
@@ -1001,6 +1002,16 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "variant_count"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aae2faf80ac463422992abf4de234731279c058aaf33171ca70277c98406b124"
+dependencies = [
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "vcpkg"
 version = "0.2.15"
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index af1ec561..f332a0fd 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -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 = "f1a0bb7fbec97dd84e35a40e8be01cf5018f2f9e" }
+mmtk = { git = "https://github.com/qinsoon/mmtk-core.git", rev = "cc405182954c24d3bd2d9cb61f4131080a7ccd4a" }
 # 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/src/scanning.rs b/mmtk/src/scanning.rs
index 7640ad87..e3e8b406 100644
--- a/mmtk/src/scanning.rs
+++ b/mmtk/src/scanning.rs
@@ -87,7 +87,7 @@ impl Scanning<JuliaVM> for VMScanning {
         let sweep_malloced_arrays_work = SweepMallocedArrays::new();
         memory_manager::add_work_packet(
             &SINGLETON,
-            WorkBucketStage::Compact,
+            WorkBucketStage::Release,
             sweep_malloced_arrays_work,
         );
     }