diff --git a/.github/scripts/ci-test-global-alloc-bit.sh b/.github/scripts/ci-test-vo-bit.sh
similarity index 99%
rename from .github/scripts/ci-test-global-alloc-bit.sh
rename to .github/scripts/ci-test-vo-bit.sh
index d38c71bf..7c8d43fb 100755
--- a/.github/scripts/ci-test-global-alloc-bit.sh
+++ b/.github/scripts/ci-test-vo-bit.sh
@@ -5,7 +5,7 @@ set -xe
 unset JAVA_TOOL_OPTIONS
 
 export MMTK_EXTREME_ASSERTIONS=0
-export GLOBAL_ALLOC_BIT=1
+export VO_BIT=1
 . $(dirname "$0")/ci-build.sh
 
 cd $OPENJDK_PATH
diff --git a/.github/scripts/ci-test.sh b/.github/scripts/ci-test.sh
index 1de23a83..6112d1b9 100755
--- a/.github/scripts/ci-test.sh
+++ b/.github/scripts/ci-test.sh
@@ -10,6 +10,6 @@ cd $cur
 cd $cur
 ./ci-test-assertions.sh
 cd $cur
-./ci-test-global-alloc-bit.sh
+./ci-test-vo-bit.sh
 cd $cur
 ./ci-test-malloc-mark-sweep.sh
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 38b9252f..7c86df77 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,8 +24,8 @@ jobs:
         run: |
           ./.github/scripts/ci-build.sh
           ./.github/scripts/ci-test-only-normal.sh
-      - name: DaCapo Tests with global allocation bit
-        run: ./.github/scripts/ci-test-global-alloc-bit.sh
+      - name: DaCapo Tests with valid object bit (VO bit)
+        run: ./.github/scripts/ci-test-vo-bit.sh
       - name: DaCapo Tests with malloc Mark-Sweep
         run: ./.github/scripts/ci-test-malloc-mark-sweep.sh
 
diff --git a/README.md b/README.md
index bb7c89bd..6e5c071e 100644
--- a/README.md
+++ b/README.md
@@ -197,12 +197,14 @@ building OpenJDK, we can change its location to be in the object's header:
 $ MARK_IN_HEADER=1 make CONF=linux-x86_64-normal-server-$DEBUG_LEVEL THIRD_PARTY_HEAP=$PWD/../mmtk-openjdk/openjdk
 ```
 
-### Alloc bit
-To support the `global_alloc_bit` feature in mmtk-core, you can set the environment variable `GLOBAL_ALLOC_BIT=1` when
-building OpenJDK. This will set the feature for mmtk-core, as well as compiling the fastpath for the alloc bit.
+### Valid object bit
+
+To support the `vo_bit` (valid object bit) feature in mmtk-core, you can set the
+environment variable `VO_BIT=1` when building OpenJDK. This will set the feature
+for mmtk-core, as well as compiling the fastpath for the VO bit.
 
 ```console
-$ GLOBAL_ALLOC_BIT=1 make CONF=linux-x86_64-normal-server-$DEBUG_LEVEL THIRD_PARTY_HEAP=$PWD/../mmtk-openjdk/openjdk
+$ VO_BIT=1 make CONF=linux-x86_64-normal-server-$DEBUG_LEVEL THIRD_PARTY_HEAP=$PWD/../mmtk-openjdk/openjdk
 ```
 
 ## Test
diff --git a/mmtk/Cargo.lock b/mmtk/Cargo.lock
index 0f560737..b95913e7 100644
--- a/mmtk/Cargo.lock
+++ b/mmtk/Cargo.lock
@@ -419,7 +419,7 @@ dependencies = [
 [[package]]
 name = "mmtk"
 version = "0.18.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=f8469b0a019bea58cba26e9fb5c70fb7398ccd31#f8469b0a019bea58cba26e9fb5c70fb7398ccd31"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=df146b7af6cf41cc7d6996e1ca538fd2b32950f5#df146b7af6cf41cc7d6996e1ca538fd2b32950f5"
 dependencies = [
  "atomic",
  "atomic-traits",
@@ -448,7 +448,7 @@ dependencies = [
 [[package]]
 name = "mmtk-macros"
 version = "0.18.0"
-source = "git+https://github.com/mmtk/mmtk-core.git?rev=f8469b0a019bea58cba26e9fb5c70fb7398ccd31#f8469b0a019bea58cba26e9fb5c70fb7398ccd31"
+source = "git+https://github.com/mmtk/mmtk-core.git?rev=df146b7af6cf41cc7d6996e1ca538fd2b32950f5#df146b7af6cf41cc7d6996e1ca538fd2b32950f5"
 dependencies = [
  "proc-macro-error",
  "proc-macro2",
diff --git a/mmtk/Cargo.toml b/mmtk/Cargo.toml
index f99f27c0..cae04d45 100644
--- a/mmtk/Cargo.toml
+++ b/mmtk/Cargo.toml
@@ -30,7 +30,7 @@ once_cell = "1.10.0"
 # - 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 = "f8469b0a019bea58cba26e9fb5c70fb7398ccd31" }
+mmtk = { git = "https://github.com/mmtk/mmtk-core.git", rev = "df146b7af6cf41cc7d6996e1ca538fd2b32950f5" }
 # Uncomment the following to build locally
 # mmtk = { path = "../repos/mmtk-core" }
 
@@ -42,9 +42,9 @@ default = []
 mmtk_extreme_assertions = ["mmtk/extreme_assertions"]
 nogc_lock_free = ["mmtk/nogc_lock_free"]
 nogc_no_zeroing = ["mmtk/nogc_no_zeroing"]
-# Use the env var GLOBAL_ALLOC_BIT=1 when building OpenJDK so the fastpath for setting the alloc bit will be compiled in.
+# Use the env var VO_BIT=1 when building OpenJDK so the fastpath for setting the alloc bit will be compiled in.
 # See README.
-global_alloc_bit = ["mmtk/global_alloc_bit"]
+vo_bit = ["mmtk/vo_bit"]
 
 # This compile time constant places the mark bit in the header of the object instead of on the side.
 mark_bit_in_header = []
diff --git a/mmtk/src/lib.rs b/mmtk/src/lib.rs
index 45820e47..7bca0753 100644
--- a/mmtk/src/lib.rs
+++ b/mmtk/src/lib.rs
@@ -108,8 +108,8 @@ pub static GLOBAL_SIDE_METADATA_VM_BASE_ADDRESS: uintptr_t =
     mmtk::util::metadata::side_metadata::GLOBAL_SIDE_METADATA_VM_BASE_ADDRESS.as_usize();
 
 #[no_mangle]
-pub static GLOBAL_ALLOC_BIT_ADDRESS: uintptr_t =
-    mmtk::util::metadata::side_metadata::ALLOC_SIDE_METADATA_ADDR.as_usize();
+pub static VO_BIT_ADDRESS: uintptr_t =
+    mmtk::util::metadata::side_metadata::VO_BIT_SIDE_METADATA_ADDR.as_usize();
 
 #[no_mangle]
 pub static FREE_LIST_ALLOCATOR_SIZE: uintptr_t =
diff --git a/openjdk/CompileThirdPartyHeap.gmk b/openjdk/CompileThirdPartyHeap.gmk
index 7224526a..e946eb7e 100644
--- a/openjdk/CompileThirdPartyHeap.gmk
+++ b/openjdk/CompileThirdPartyHeap.gmk
@@ -19,11 +19,11 @@ ifdef MMTK_PLAN
   GC_FEATURES=--features $(MMTK_PLAN)
 endif
 
-ifeq ($(GLOBAL_ALLOC_BIT), 1)
+ifeq ($(VO_BIT), 1)
   ifndef GC_FEATURES
-    GC_FEATURES=--features global_alloc_bit
+    GC_FEATURES=--features vo_bit
   else
-    GC_FEATURES:=$(strip $(GC_FEATURES))",global_alloc_bit"
+    GC_FEATURES:=$(strip $(GC_FEATURES))",vo_bit"
   endif
 endif
 
@@ -79,8 +79,8 @@ FORCE:
 TARGETS += $(LIB_MMTK)
 JVM_SRC_DIRS += $(MMTK_CPP_ROOT) $(MMTK_CPP_ROOT)/barriers
 JVM_CFLAGS += -std=c++11 -DINCLUDE_THIRD_PARTY_HEAP -DTHIRD_PARTY_HEAP_SRC=$(MMTK_CPP_ROOT)
-ifeq ($(GLOBAL_ALLOC_BIT), 1)
-  JVM_CFLAGS += -DMMTK_ENABLE_GLOBAL_ALLOC_BIT
+ifeq ($(VO_BIT), 1)
+  JVM_CFLAGS += -DMMTK_ENABLE_VO_BIT
 endif
 
 $(BUILD_LIBJVM): $(LIB_MMTK)
diff --git a/openjdk/mmtk.h b/openjdk/mmtk.h
index b1da9454..a2c3d9c9 100644
--- a/openjdk/mmtk.h
+++ b/openjdk/mmtk.h
@@ -20,7 +20,7 @@ typedef enum {
 
 extern const uintptr_t GLOBAL_SIDE_METADATA_BASE_ADDRESS;
 extern const uintptr_t GLOBAL_SIDE_METADATA_VM_BASE_ADDRESS;
-extern const uintptr_t GLOBAL_ALLOC_BIT_ADDRESS;
+extern const uintptr_t VO_BIT_ADDRESS;
 extern const size_t MMTK_MARK_COMPACT_HEADER_RESERVED_IN_BYTES;
 extern const uintptr_t FREE_LIST_ALLOCATOR_SIZE;
 
diff --git a/openjdk/mmtkBarrierSet.hpp b/openjdk/mmtkBarrierSet.hpp
index efced87a..07990706 100644
--- a/openjdk/mmtkBarrierSet.hpp
+++ b/openjdk/mmtkBarrierSet.hpp
@@ -40,7 +40,7 @@
 #define MMTK_ENABLE_ALLOCATION_FASTPATH true
 #define MMTK_ENABLE_BARRIER_FASTPATH true
 
-const intptr_t ALLOC_BIT_BASE_ADDRESS = GLOBAL_ALLOC_BIT_ADDRESS;
+const intptr_t VO_BIT_BASE_ADDRESS = VO_BIT_ADDRESS;
 
 struct MMTkAllocatorOffsets {
   int tlab_top_offset;
diff --git a/openjdk/mmtkBarrierSetAssembler_x86.cpp b/openjdk/mmtkBarrierSetAssembler_x86.cpp
index cb06763b..dc59274e 100644
--- a/openjdk/mmtkBarrierSetAssembler_x86.cpp
+++ b/openjdk/mmtkBarrierSetAssembler_x86.cpp
@@ -98,11 +98,11 @@ void MMTkBarrierSetAssembler::eden_allocate(MacroAssembler* masm, Register threa
     __ jcc(Assembler::above, slow_case);
     // lab.cursor = end
     __ movptr(cursor, end);
-  bool enable_global_alloc_bit = false;
-  #ifdef MMTK_ENABLE_GLOBAL_ALLOC_BIT
-  enable_global_alloc_bit = true;
+  bool enable_vo_bit = false;
+  #ifdef MMTK_ENABLE_VO_BIT
+  enable_vo_bit = true;
   #endif
-  if (enable_global_alloc_bit || selector.tag == TAG_MARK_COMPACT) {
+  if (enable_vo_bit || selector.tag == TAG_MARK_COMPACT) {
     Register tmp3 = rdi;
     Register tmp2 = rscratch1;
     assert_different_registers(obj, tmp2, tmp3, rcx);
@@ -110,7 +110,7 @@ void MMTkBarrierSetAssembler::eden_allocate(MacroAssembler* masm, Register threa
     // tmp2 = load-byte (SIDE_METADATA_BASE_ADDRESS + (obj >> 6));
     __ movptr(tmp3, obj);
     __ shrptr(tmp3, 6);
-    __ movptr(tmp2, ALLOC_BIT_BASE_ADDRESS);
+    __ movptr(tmp2, VO_BIT_BASE_ADDRESS);
     __ movb(tmp2, Address(tmp2, tmp3));
     // tmp3 = 1 << ((obj >> 3) & 7)
     //   1. rcx = (obj >> 3) & 7
@@ -126,7 +126,7 @@ void MMTkBarrierSetAssembler::eden_allocate(MacroAssembler* masm, Register threa
     // store-byte tmp2 (SIDE_METADATA_BASE_ADDRESS + (obj >> 6))
     __ movptr(tmp3, obj);
     __ shrptr(tmp3, 6);
-    __ movptr(rcx, ALLOC_BIT_BASE_ADDRESS);
+    __ movptr(rcx, VO_BIT_BASE_ADDRESS);
     __ movb(Address(rcx, tmp3), tmp2);
   }
 
diff --git a/openjdk/mmtkBarrierSetC2.cpp b/openjdk/mmtkBarrierSetC2.cpp
index d885fe97..b58e433d 100644
--- a/openjdk/mmtkBarrierSetC2.cpp
+++ b/openjdk/mmtkBarrierSetC2.cpp
@@ -272,14 +272,14 @@ void MMTkBarrierSetC2::expand_allocate(PhaseMacroExpand* x,
     fast_oop_ctrl = needgc_false; // No contention, so this is the fast path
     fast_oop_rawmem = store_eden_top;
 
-    bool enable_global_alloc_bit = false;
-    #ifdef MMTK_ENABLE_GLOBAL_ALLOC_BIT
-    enable_global_alloc_bit = true;
+    bool enable_vo_bit = false;
+    #ifdef MMTK_ENABLE_VO_BIT
+    enable_vo_bit = true;
     #endif
-  if (enable_global_alloc_bit || selector.tag == TAG_MARK_COMPACT) {
+  if (enable_vo_bit || selector.tag == TAG_MARK_COMPACT) {
     // set the alloc bit:
     // intptr_t addr = (intptr_t) (void*) fast_oop;
-    // uint8_t* meta_addr = (uint8_t*) (ALLOC_BIT_BASE_ADDRESS + (addr >> 6));
+    // uint8_t* meta_addr = (uint8_t*) (VO_BIT_BASE_ADDRESS + (addr >> 6));
     // intptr_t shift = (addr >> 3) & 0b111;
     // uint8_t byte_val = *meta_addr;
     // uint8_t new_byte_val = byte_val | (1 << shift);
@@ -293,7 +293,7 @@ void MMTkBarrierSetC2::expand_allocate(PhaseMacroExpand* x,
     Node *meta_offset = new URShiftLNode(obj_addr, addr_shift);
     x->transform_later(meta_offset);
 
-    Node *meta_base = ConLNode::make(ALLOC_BIT_BASE_ADDRESS);
+    Node *meta_base = ConLNode::make(VO_BIT_BASE_ADDRESS);
     x->transform_later(meta_base);
 
     Node *meta_addr = new AddLNode(meta_base, meta_offset);
@@ -329,10 +329,10 @@ void MMTkBarrierSetC2::expand_allocate(PhaseMacroExpand* x,
     Node *new_meta_val = new OrINode(meta_val, set_bit);
     x->transform_later(new_meta_val);
 
-    Node *set_alloc_bit = new StoreBNode(fast_oop_ctrl, fast_oop_rawmem, meta_addr_p, TypeRawPtr::BOTTOM, new_meta_val, MemNode::unordered);
-    x->transform_later(set_alloc_bit);
+    Node *set_vo_bit = new StoreBNode(fast_oop_ctrl, fast_oop_rawmem, meta_addr_p, TypeRawPtr::BOTTOM, new_meta_val, MemNode::unordered);
+    x->transform_later(set_vo_bit);
 
-    fast_oop_rawmem = set_alloc_bit;
+    fast_oop_rawmem = set_vo_bit;
   }
 
     InitializeNode* init = alloc->initialization();