diff --git a/vmkit/src/bdwgc_shim.rs b/vmkit/src/bdwgc_shim.rs
index d3a9fa1..7bd4c97 100644
--- a/vmkit/src/bdwgc_shim.rs
+++ b/vmkit/src/bdwgc_shim.rs
@@ -462,21 +462,21 @@ static CONSERVATIVE_METADATA: GCMetadata<BDWGC> = GCMetadata {
     }),
 };
 
-impl FromBitfield<u64> for BDWGCMetadata {
-    fn from_bitfield(value: u64) -> Self {
+impl FromBitfield<usize> for BDWGCMetadata {
+    fn from_bitfield(value: usize) -> Self {
         Self {
             meta: value as usize,
         }
     }
 
     fn from_i64(value: i64) -> Self {
-        Self::from_bitfield(value as u64)
+        Self::from_bitfield(value as usize)
     }
 }
 
-impl ToBitfield<u64> for BDWGCMetadata {
-    fn to_bitfield(self) -> u64 {
-        self.meta as u64
+impl ToBitfield<usize> for BDWGCMetadata {
+    fn to_bitfield(self) -> usize {
+        self.meta as usize
     }
 
     fn one() -> Self {
diff --git a/vmkit/src/main.rs b/vmkit/src/main.rs
index f328e4d..35f4ae6 100644
--- a/vmkit/src/main.rs
+++ b/vmkit/src/main.rs
@@ -1 +1,9 @@
-fn main() {}
+use easy_bitfield::BitFieldTrait;
+use vmkit::object_model::header::{HashState, HashStateField};
+
+fn main() {
+    let encoded = HashStateField::encode(HashState::HashedAndMoved);
+    println!("{:x}", encoded);
+    println!("{}", HashStateField::NEXT_BIT);
+    println!("{:?}", HashStateField::decode(encoded));
+}
diff --git a/vmkit/src/object_model/header.rs b/vmkit/src/object_model/header.rs
index dd7128f..37cf2d1 100644
--- a/vmkit/src/object_model/header.rs
+++ b/vmkit/src/object_model/header.rs
@@ -11,10 +11,10 @@ pub const OBJECT_REF_OFFSET: isize = 8;
 pub const OBJECT_HEADER_OFFSET: isize = -OBJECT_REF_OFFSET;
 pub const HASHCODE_OFFSET: isize = -(OBJECT_REF_OFFSET + size_of::<usize>() as isize);
 
-pub const METADATA_BIT_LIMIT: usize = if ADDRESS_BASED_HASHING { 60 } else { 63 };
+pub const METADATA_BIT_LIMIT: usize = if ADDRESS_BASED_HASHING { usize::BITS as usize - 2 } else { usize::BITS as usize };
 
-pub type MetadataField = BitField<u64, usize, 0, METADATA_BIT_LIMIT, false>;
-pub type HashStateField = BitField<u64, HashState, { MetadataField::NEXT_BIT }, 2, false>;
+pub type MetadataField = BitField<usize, usize, 0, METADATA_BIT_LIMIT, false>;
+pub type HashStateField = BitField<usize, HashState, { MetadataField::NEXT_BIT }, 2, false>;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum HashState {
@@ -23,8 +23,8 @@ pub enum HashState {
     HashedAndMoved,
 }
 
-impl FromBitfield<u64> for HashState {
-    fn from_bitfield(value: u64) -> Self {
+impl FromBitfield<usize> for HashState {
+    fn from_bitfield(value: usize) -> Self {
         match value {
             0 => Self::Unhashed,
             1 => Self::Hashed,
@@ -43,8 +43,8 @@ impl FromBitfield<u64> for HashState {
     }
 }
 
-impl ToBitfield<u64> for HashState {
-    fn to_bitfield(self) -> u64 {
+impl ToBitfield<usize> for HashState {
+    fn to_bitfield(self) -> usize {
         match self {
             Self::Unhashed => 0,
             Self::Hashed => 1,
@@ -62,7 +62,7 @@ impl ToBitfield<u64> for HashState {
 }
 
 pub struct HeapObjectHeader<VM: VirtualMachine> {
-    pub metadata: AtomicBitfieldContainer<u64>,
+    pub metadata: AtomicBitfieldContainer<usize>,
     pub marker: PhantomData<VM>,
 }
 
diff --git a/vmkit/src/object_model/metadata.rs b/vmkit/src/object_model/metadata.rs
index d49fee4..154ff6a 100644
--- a/vmkit/src/object_model/metadata.rs
+++ b/vmkit/src/object_model/metadata.rs
@@ -32,7 +32,7 @@ pub enum TraceCallback<VM: VirtualMachine> {
 ///
 /// Types which implement `Metadata` must also be convertible to and from bitfields.
 pub trait Metadata<VM: VirtualMachine>:
-    ToBitfield<u64> + FromBitfield<u64> + ToSlot<VM::Slot>
+    ToBitfield<usize> + FromBitfield<usize> + ToSlot<VM::Slot>
 {
     /// Size of the metadata in bits. Must be `<= 62`.
     const METADATA_BIT_SIZE: usize;
@@ -82,16 +82,16 @@ macro_rules! make_uncooperative_metadata {
                 unreachable!()
             }
         }
-        impl<VM: $crate::VirtualMachine> $crate::object_model::metadata::ToBitfield<u64> for $name {
-            fn to_bitfield(self) -> u64 {
-                self.wsize as u64
+        impl<VM: $crate::VirtualMachine> $crate::object_model::metadata::ToBitfield<usize> for $name {
+            fn to_bitfield(self) -> usize {
+                self.wsize as usize
             }
         }
 
-        impl<VM: $crate::VirtualMachine> $crate::object_model::metadata::FromBitfield<u64>
+        impl<VM: $crate::VirtualMachine> $crate::object_model::metadata::FromBitfield<usize>
             for $name
         {
-            fn from_bitfield(value: u64) -> Self {
+            fn from_bitfield(value: usize) -> Self {
                 Self {
                     wsize: value as usize,
                 }
@@ -100,9 +100,9 @@ macro_rules! make_uncooperative_metadata {
     };
 }
 
-impl<VM: VirtualMachine> ToBitfield<u64> for &'static GCMetadata<VM> {
-    fn to_bitfield(self) -> u64 {
-        let res = self as *const GCMetadata<VM> as usize as u64;
+impl<VM: VirtualMachine> ToBitfield<usize> for &'static GCMetadata<VM> {
+    fn to_bitfield(self) -> usize {
+        let res = self as *const GCMetadata<VM> as usize as usize;
         res
     }
 
@@ -115,8 +115,8 @@ impl<VM: VirtualMachine> ToBitfield<u64> for &'static GCMetadata<VM> {
     }
 }
 
-impl<VM: VirtualMachine> FromBitfield<u64> for &'static GCMetadata<VM> {
-    fn from_bitfield(value: u64) -> Self {
+impl<VM: VirtualMachine> FromBitfield<usize> for &'static GCMetadata<VM> {
+    fn from_bitfield(value: usize) -> Self {
         unsafe { &*(value as usize as *const GCMetadata<VM>) }
     }