diff --git a/src/lib.rs b/src/lib.rs
index 008795c..6d3dc87 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,6 +5,7 @@
 mod builtins;
 mod bytecode;
 mod ty;
+mod stack;
 
 pub mod compile;
 pub mod error;
diff --git a/src/vm/stack.rs b/src/stack.rs
similarity index 76%
rename from src/vm/stack.rs
rename to src/stack.rs
index 915ef82..21e5e83 100644
--- a/src/vm/stack.rs
+++ b/src/stack.rs
@@ -1,14 +1,11 @@
-use std::mem::{MaybeUninit, replace, size_of, transmute};
+use std::mem::{MaybeUninit, replace, transmute};
 use std::ops::Deref;
 
 use crate::error::*;
-use crate::ty::internal::Value;
 
-pub const STACK_SIZE: usize = 8 * 1024 / size_of::<Value>();
-
-pub struct Stack<'vm, const CAP: usize> {
+pub struct Stack<T, const CAP: usize> {
     // items: Box<[MaybeUninit<Value<'vm>>; CAP]>,
-    items: [MaybeUninit<Value<'vm>>; CAP],
+    items: [MaybeUninit<T>; CAP],
     top: usize,
 }
 
@@ -22,7 +19,7 @@ macro_rules! into {
     };
 }
 
-impl<'vm, const CAP: usize> Stack<'vm, CAP> {
+impl<T, const CAP: usize> Stack<T, CAP> {
     pub fn new() -> Self {
         Stack {
             items: [const { MaybeUninit::uninit() }; CAP],
@@ -30,7 +27,7 @@ impl<'vm, const CAP: usize> Stack<'vm, CAP> {
         }
     }
 
-    pub fn push(&mut self, item: Value<'vm>) -> Result<()> {
+    pub fn push(&mut self, item: T) -> Result<()> {
         self.items
             .get_mut(self.top)
             .map_or_else(
@@ -42,7 +39,7 @@ impl<'vm, const CAP: usize> Stack<'vm, CAP> {
         Ok(())
     }
 
-    pub fn pop(&mut self) -> Value<'vm> {
+    pub fn pop(&mut self) -> T {
         self.top -= 1;
         let item = self.items.get_mut(self.top).unwrap();
 
@@ -52,7 +49,7 @@ impl<'vm, const CAP: usize> Stack<'vm, CAP> {
         unsafe { replace(item, MaybeUninit::uninit()).assume_init() }
     }
 
-    pub fn tos(&self) -> Result<&Value<'vm>> {
+    pub fn tos(&self) -> Result<&T> {
         if self.top == 0 {
             panic!("stack empty")
         } else {
@@ -60,7 +57,7 @@ impl<'vm, const CAP: usize> Stack<'vm, CAP> {
         }
     }
 
-    pub fn tos_mut(&mut self) -> Result<&mut Value<'vm>> {
+    pub fn tos_mut(&mut self) -> Result<&mut T> {
         if self.top == 0 {
             panic!("stack empty")
         } else {
@@ -69,14 +66,14 @@ impl<'vm, const CAP: usize> Stack<'vm, CAP> {
     }
 }
 
-impl<'vm, const CAP: usize> Deref for Stack<'vm, CAP> {
-    type Target = [Value<'vm>];
+impl<T, const CAP: usize> Deref for Stack<T, CAP> {
+    type Target = [T];
     fn deref(&self) -> &Self::Target {
         into!(&self.items[0..self.top])
     }
 }
 
-impl<const CAP: usize> Drop for Stack<'_, CAP> {
+impl<T, const CAP: usize> Drop for Stack<T, CAP> {
     fn drop(&mut self) {
         self.items.as_mut_slice()[0..self.top]
             .iter_mut()
diff --git a/src/vm/mod.rs b/src/vm/mod.rs
index a2a14cf..f29958c 100644
--- a/src/vm/mod.rs
+++ b/src/vm/mod.rs
@@ -7,18 +7,19 @@ use crate::ty::common::Symbol;
 use crate::ty::internal::*;
 use crate::ty::public as p;
 
-use stack::{STACK_SIZE, Stack};
+use crate::stack::Stack;
 
 pub use env::Env;
 pub use jit::JITContext;
 
 mod env;
 mod jit;
-mod stack;
 
 #[cfg(test)]
 mod test;
 
+const STACK_SIZE: usize = 8 * 1024 / size_of::<Value>();
+
 pub fn run(prog: Program, jit: JITContext<'_>) -> Result<p::Value> {
     let vm = VM::new(
         prog.thunks,
@@ -57,7 +58,7 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
     }
 
     pub fn eval(&'vm self, opcodes: OpCodes, env: Rc<Env<'vm>>) -> Result<Value<'vm>> {
-        let mut stack = Stack::<STACK_SIZE>::new();
+        let mut stack = Stack::<_, STACK_SIZE>::new();
         let mut iter = opcodes.into_iter();
         while let Some(opcode) = iter.next() {
             let jmp = self.single_op(opcode, &mut stack, &env)?;
@@ -75,7 +76,7 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
     fn single_op<'s, const CAP: usize>(
         &'vm self,
         opcode: OpCode,
-        stack: &'s mut Stack<'vm, CAP>,
+        stack: &'s mut Stack<Value<'vm>, CAP>,
         env: &Rc<Env<'vm>>,
     ) -> Result<usize> {
         match opcode {