diff --git a/Cargo.lock b/Cargo.lock
index 091d8b8..4335382 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -45,6 +45,15 @@ version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5c8214115b7bf84099f1309324e63141d4c5d7cc26862f97a0a857dbefe165bd"
 
+[[package]]
+name = "bumpalo"
+version = "3.17.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1628fb46dfa0b37568d12e5edd512553eccf6a22a78e8bde00bb4aed84d5bdbf"
+dependencies = [
+ "allocator-api2",
+]
+
 [[package]]
 name = "cc"
 version = "1.2.21"
@@ -307,6 +316,7 @@ dependencies = [
 name = "nixjit"
 version = "0.0.0"
 dependencies = [
+ "bumpalo",
  "derive_more",
  "ecow",
  "hashbrown 0.15.3",
diff --git a/Cargo.toml b/Cargo.toml
index 5465aa4..586ff2c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -25,11 +25,11 @@ rnix = "0.12"
 thiserror = "2.0"
 itertools = "0.14"
 rpds = "1.1"
-derive_more = { version = "2.0", features = [ "full" ] }
+derive_more = { version = "2.0", features = ["full"] }
 ecow = "0.2"
 regex = "1.11"
 hashbrown = "0.15"
-
 inkwell = { version = "0.6.0", features = ["llvm18-1"] }
+bumpalo = { version = "3.17", features = ["allocator-api2"] }
 
 rustyline = { version = "15.0", optional = true }
diff --git a/src/builtins/mod.rs b/src/builtins/mod.rs
index 9c0825a..c7c21a2 100644
--- a/src/builtins/mod.rs
+++ b/src/builtins/mod.rs
@@ -1,15 +1,12 @@
-use hashbrown::HashMap;
 use std::rc::Rc;
 
+use hashbrown::HashMap;
+
 use crate::ty::common::Const;
 use crate::ty::internal::{AttrSet, PrimOp, Value};
 use crate::vm::{VM, VmEnv};
 
 pub fn env<'jit, 'vm>(vm: &'vm VM<'jit>) -> VmEnv<'jit, 'vm> {
-    let mut env_map = HashMap::new();
-    env_map.insert(vm.new_sym("true"), Value::Const(Const::Bool(true)));
-    env_map.insert(vm.new_sym("false"), Value::Const(Const::Bool(false)));
-
     let primops = [
         PrimOp::new("add", 2, |_, args| {
             let [mut first, second]: [Value; 2] = args.try_into().unwrap();
@@ -49,6 +46,11 @@ pub fn env<'jit, 'vm>(vm: &'vm VM<'jit>) -> VmEnv<'jit, 'vm> {
         }),
     ];
 
+    let mut env_map = HashMap::new_in(&vm.bump);
+    env_map.insert(vm.new_sym("true"), Value::Const(Const::Bool(true)));
+    env_map.insert(vm.new_sym("false"), Value::Const(Const::Bool(false)));
+
+
     let mut map = HashMap::new();
     for primop in primops {
         let primop = Rc::new(primop);
@@ -66,5 +68,5 @@ pub fn env<'jit, 'vm>(vm: &'vm VM<'jit>) -> VmEnv<'jit, 'vm> {
     let builtins = Value::AttrSet(attrs);
 
     env_map.insert(sym, builtins);
-    VmEnv::new(env_map.into())
+    VmEnv::new(vm.bump.alloc(env_map), &vm.bump)
 }
diff --git a/src/jit/helpers.rs b/src/jit/helpers.rs
index 48893a6..609bc2f 100644
--- a/src/jit/helpers.rs
+++ b/src/jit/helpers.rs
@@ -1,5 +1,3 @@
-use std::rc::Rc;
-
 use inkwell::AddressSpace;
 use inkwell::context::Context;
 use inkwell::execution_engine::ExecutionEngine;
@@ -209,9 +207,8 @@ extern "C" fn helper_debug(value: JITValue) {
 
 extern "C" fn helper_capture_env(thunk: JITValue, env: *const VmEnv) {
     let thunk = unsafe { (thunk.data.ptr as *const Thunk).as_ref().unwrap() };
-    let env = unsafe { Rc::from_raw(env) };
-    thunk.capture(env.clone());
-    std::mem::forget(env);
+    let env = unsafe { env.as_ref() }.unwrap();
+    thunk.capture(env);
 }
 
 extern "C" fn helper_neg(rhs: JITValue, _env: *const VmEnv) -> JITValue {
diff --git a/src/jit/mod.rs b/src/jit/mod.rs
index 0410d9c..a8bf29a 100644
--- a/src/jit/mod.rs
+++ b/src/jit/mod.rs
@@ -165,10 +165,10 @@ impl<'vm, 'ctx: 'vm> JITContext<'ctx> {
             .unwrap()
     }
 
-    pub fn compile_function(
+    pub fn compile_function<'bump>(
         &self,
         func: &Func,
-        vm: &'vm VM<'_>,
+        vm: &'vm VM<'ctx>,
     ) -> Result<JitFunction<'ctx, JITFunc<'ctx, 'vm>>> {
         let mut stack = Stack::<_, STACK_SIZE>::new();
         let mut iter = func.opcodes.iter().copied();
diff --git a/src/jit/test.rs b/src/jit/test.rs
index 908e031..fd92ca4 100644
--- a/src/jit/test.rs
+++ b/src/jit/test.rs
@@ -2,6 +2,7 @@
 
 extern crate test;
 
+use bumpalo::Bump;
 use hashbrown::{HashMap, HashSet};
 
 use inkwell::context::Context;
@@ -30,11 +31,12 @@ fn test_expr(expr: &str, expected: Value) {
         prog.symbols.into(),
         prog.symmap.into(),
         prog.consts,
+        Bump::new(),
         jit,
     );
     let env = env(&vm);
     let value = vm
-        .eval(prog.top_level.into_iter(), env.into())
+        .eval(prog.top_level.into_iter(), vm.bump.alloc(env))
         .unwrap()
         .to_public(&vm, &mut HashSet::new());
     assert_eq!(value, expected);
diff --git a/src/lib.rs b/src/lib.rs
index 1b27b13..2b780a5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,5 +1,6 @@
 #![cfg_attr(test, feature(test))]
 #![allow(dead_code)]
+#![feature(iter_collect_into)]
 
 mod builtins;
 mod bytecode;
diff --git a/src/ty/internal/attrset.rs b/src/ty/internal/attrset.rs
index b1c6c8c..74e4105 100644
--- a/src/ty/internal/attrset.rs
+++ b/src/ty/internal/attrset.rs
@@ -52,10 +52,10 @@ impl<'jit: 'vm, 'vm> AttrSet<'jit, 'vm> {
         self.data.get(&sym).is_some()
     }
 
-    pub fn capture(&mut self, env: &Rc<VmEnv<'jit, 'vm>>) {
+    pub fn capture(&mut self, env: &'vm VmEnv<'jit, 'vm>) {
         self.data.iter().for_each(|(_, v)| {
             if let Value::Thunk(ref thunk) = v.clone() {
-                thunk.capture(Rc::clone(env));
+                thunk.capture(env);
             }
         })
     }
diff --git a/src/ty/internal/func.rs b/src/ty/internal/func.rs
index aaa804e..f97e69f 100644
--- a/src/ty/internal/func.rs
+++ b/src/ty/internal/func.rs
@@ -1,5 +1,4 @@
 use std::cell::{Cell, OnceCell};
-use std::rc::Rc;
 
 use derive_more::Constructor;
 use hashbrown::HashMap;
@@ -46,7 +45,7 @@ impl From<ir::Param> for Param {
 #[derive(Debug, Clone, Constructor)]
 pub struct Func<'jit: 'vm, 'vm> {
     pub func: &'vm BFunc,
-    pub env: Rc<VmEnv<'jit, 'vm>>,
+    pub env: &'vm VmEnv<'jit, 'vm>,
     pub compiled: OnceCell<JitFunction<'jit, JITFunc<'jit, 'vm>>>,
     pub count: Cell<usize>,
 }
@@ -55,16 +54,16 @@ impl<'vm, 'jit: 'vm> Func<'jit, 'vm> {
     pub fn call(&self, vm: &'vm VM<'jit>, arg: Value<'jit, 'vm>) -> Result<Value<'jit, 'vm>> {
         use Param::*;
 
-        let mut env = self.env.clone();
-        match self.func.param.clone() {
-            Ident(ident) => env.enter_arg(ident, arg),
+        let mut env = self.env;
+        env = match self.func.param.clone() {
+            Ident(ident) => env.enter_arg(ident, arg, &vm.bump),
             Formals {
                 formals,
                 ellipsis,
                 alias,
             } => {
                 let arg = arg.unwrap_attr_set();
-                let mut new = HashMap::with_capacity(formals.len() + alias.iter().len());
+                let mut new = HashMap::with_capacity_in(formals.len() + alias.iter().len(), &vm.bump);
                 if !ellipsis
                     && arg
                         .as_inner()
@@ -87,7 +86,7 @@ impl<'vm, 'jit: 'vm> Func<'jit, 'vm> {
                 if let Some(alias) = alias {
                     new.insert(alias, Value::AttrSet(arg));
                 }
-                env.enter_let(new.into())
+                env.enter_let(vm.bump.alloc(new), &vm.bump)
             }
         };
 
@@ -95,14 +94,11 @@ impl<'vm, 'jit: 'vm> Func<'jit, 'vm> {
         self.count.replace(count + 1);
         if count >= 1 {
             let compiled = self.compiled.get_or_init(|| vm.compile_func(self.func));
-            let env = Rc::into_raw(env);
+            let env = env as *const _;
             let ret = unsafe { compiled.call(vm as *const VM, env) };
-            unsafe {
-                Rc::decrement_strong_count(env);
-            }
             return Ok(ret.into());
         }
-        vm.eval(self.func.opcodes.iter().copied(), env)
+        vm.eval(self.func.opcodes.iter().copied(), vm.bump.alloc(env))
     }
 }
 
diff --git a/src/ty/internal/mod.rs b/src/ty/internal/mod.rs
index 13db9fd..e4b4597 100644
--- a/src/ty/internal/mod.rs
+++ b/src/ty/internal/mod.rs
@@ -467,17 +467,11 @@ pub struct Thunk<'jit, 'vm> {
 
 #[derive(Debug, IsVariant, Unwrap, Clone)]
 pub enum _Thunk<'jit, 'vm> {
-    Code(&'vm OpCodes, OnceCell<EnvRef<'jit, 'vm>>),
+    Code(&'vm OpCodes, OnceCell<&'vm VmEnv<'jit, 'vm>>),
     SuspendedFrom(*const Thunk<'jit, 'vm>),
     Value(Value<'jit, 'vm>),
 }
 
-#[derive(Debug, IsVariant, Unwrap, Clone)]
-pub enum EnvRef<'jit, 'vm> {
-    Strong(Rc<VmEnv<'jit, 'vm>>),
-    Weak(Weak<VmEnv<'jit, 'vm>>),
-}
-
 impl<'jit, 'vm> Thunk<'jit, 'vm> {
     pub fn new(opcodes: &'vm OpCodes) -> Self {
         Thunk {
@@ -485,15 +479,9 @@ impl<'jit, 'vm> Thunk<'jit, 'vm> {
         }
     }
 
-    pub fn capture(&self, env: Rc<VmEnv<'jit, 'vm>>) {
+    pub fn capture(&self, env: &'vm VmEnv<'jit, 'vm>) {
         if let _Thunk::Code(_, envcell) = &*self.thunk.borrow() {
-            envcell.get_or_init(|| EnvRef::Strong(env));
-        }
-    }
-
-    pub fn capture_weak(&self, env: Weak<VmEnv<'jit, 'vm>>) {
-        if let _Thunk::Code(_, envcell) = &*self.thunk.borrow() {
-            envcell.get_or_init(|| EnvRef::Weak(env));
+            envcell.get_or_init(|| env);
         }
     }
 
@@ -519,10 +507,7 @@ impl<'jit, 'vm> Thunk<'jit, 'vm> {
             _Thunk::SuspendedFrom(self as *const Thunk),
         )
         .unwrap_code();
-        let env = match env.get().unwrap() {
-            EnvRef::Strong(env) => env.clone(),
-            EnvRef::Weak(env) => env.upgrade().unwrap(),
-        };
+        let env = env.get().unwrap();
         let value = vm.eval(opcodes.iter().copied(), env)?;
         let _ = std::mem::replace(&mut *self.thunk.borrow_mut(), _Thunk::Value(value));
         Ok(match unsafe { &*(&*self.thunk.borrow() as *const _) } {
diff --git a/src/vm/env.rs b/src/vm/env.rs
index 2d6b9bc..b8f27fc 100644
--- a/src/vm/env.rs
+++ b/src/vm/env.rs
@@ -1,53 +1,58 @@
 use std::fmt::Debug;
-use std::{hash::Hash, rc::Rc};
+use std::hash::Hash;
 
-use hashbrown::HashMap;
+use hashbrown::{DefaultHashBuilder, HashMap};
+use bumpalo::Bump;
 
 use crate::ty::internal::Value;
 
+type Map<'bump, K, V> = HashMap<K, V, DefaultHashBuilder, &'bump Bump>;
+
 #[derive(Clone)]
-pub struct Env<K: Hash + Eq + Clone, V: Clone> {
-    let_: Rc<LetEnv<K, V>>,
-    with: Rc<With<K, V>>,
+pub struct Env<'bump, K: Hash + Eq + Clone, V: Clone> {
+    let_: &'bump LetEnv<'bump, K, V>,
+    with: &'bump With<'bump, K, V>,
+    last: Option<&'bump Env<'bump, K, V>>,
 }
 
 #[derive(Clone)]
-pub struct LetEnv<K: Hash + Eq + Clone, V: Clone> {
-    map: LetNode<K, V>,
-    last: Option<Rc<LetEnv<K, V>>>,
+pub struct LetEnv<'bump, K: Hash + Eq + Clone, V: Clone> {
+    map: LetNode<'bump, K, V>,
+    last: Option<&'bump LetEnv<'bump, K, V>>,
 }
 
-impl<K: Debug + Hash + Eq + Clone, V: Debug + Clone> Debug for Env<K, V> {
+impl<K: Debug + Hash + Eq + Clone, V: Debug + Clone> Debug for Env<'_, K, V> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("Env")
             .field("let_", &self.let_)
             .field("with", &self.with)
+            .field("last", &self.last)
             .finish()
     }
 }
 
-impl<K: Debug + Hash + Eq + Clone, V: Debug + Clone> Debug for LetEnv<K, V> {
+impl<K: Debug + Hash + Eq + Clone, V: Debug + Clone> Debug for LetEnv<'_, K, V> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("Env")
+        f.debug_struct("LetEnv")
             .field("map", &self.map)
             .field("last", &self.last)
             .finish()
     }
 }
 
-pub type VmEnv<'jit, 'vm> = Env<usize, Value<'jit, 'vm>>;
+pub type VmEnv<'jit, 'vm> = Env<'vm, usize, Value<'jit, 'vm>>;
 
 #[derive(Debug, Default, Clone)]
-pub struct With<K: Hash + Eq, V> {
-    map: Option<Rc<HashMap<K, V>>>,
-    last: Option<Rc<With<K, V>>>,
+pub struct With<'bump, K: Hash + Eq, V> {
+    map: Option<&'bump Map<'bump, K, V>>,
+    last: Option<&'bump With<'bump, K, V>>,
 }
 
 #[derive(Debug, Clone)]
-enum LetNode<K: Hash + Eq, V> {
-    Let(Rc<HashMap<K, V>>),
+enum LetNode<'bump, K: Hash + Eq + Clone, V: Clone> {
+    Let(&'bump Map<'bump, K, V>),
     SingleArg(K, V),
-    MultiArg(Rc<HashMap<K, V>>),
+    MultiArg(&'bump Map<'bump, K, V>),
 }
 
 #[derive(Debug, Clone, Copy)]
@@ -57,15 +62,15 @@ pub enum Type {
     With,
 }
 
-impl<K: Hash + Eq + Clone, V: Clone> Env<K, V> {
-    pub fn new(map: Rc<HashMap<K, V>>) -> Self {
+impl<'bump, K: Hash + Eq + Clone, V: Clone> Env<'bump, K, V> {
+    pub fn new(map: &'bump Map<'bump, K, V>, bump: &'bump Bump) -> Self {
         Self {
-            let_: LetEnv::new(map).into(),
-            with: With {
+            let_: &*bump.alloc(LetEnv::new(map)),
+            with: &*bump.alloc(With {
                 map: None,
                 last: None,
-            }
-            .into(),
+            }),
+            last: None
         }
     }
 
@@ -76,29 +81,37 @@ impl<K: Hash + Eq + Clone, V: Clone> Env<K, V> {
         self.with.lookup(symbol)
     }
 
-    pub fn enter_arg(self: &mut Rc<Self>, ident: K, val: V) {
-        Rc::make_mut(self).let_.enter_arg(ident, val);
+    pub fn enter_arg(&'bump self, ident: K, val: V, bump: &'bump Bump) -> &'bump Self {
+        &*bump.alloc(Env {
+            let_: self.let_.enter_arg(ident, val, bump),
+            with: self.with,
+            last: Some(self)
+        })
     }
 
-    pub fn enter_let(self: &mut Rc<Self>, map: Rc<HashMap<K, V>>) {
-        Rc::make_mut(self).let_.enter_let(map);
+    pub fn enter_let(&'bump self, map: &'bump Map<'bump, K, V>, bump: &'bump Bump) -> &'bump Self {
+        &*bump.alloc(Env {
+            let_: self.let_.enter_let(map, bump),
+            with: self.with,
+            last: Some(self)
+        })
     }
 
-    pub fn enter_with(self: &mut Rc<Self>, map: Rc<HashMap<K, V>>) {
-        Rc::make_mut(self).with.enter(map);
+    pub fn enter_with(&'bump self, map: &'bump Map<'bump, K, V>, bump: &'bump Bump) -> &'bump Self {
+        &*bump.alloc(Env {
+            let_: self.let_,
+            with: self.with.enter(map, bump),
+            last: Some(self)
+        })
     }
 
-    pub fn leave_let(self: &mut Rc<Self>) {
-        Rc::make_mut(self).let_.leave();
-    }
-
-    pub fn leave_with(self: &mut Rc<Self>) {
-        Rc::make_mut(self).with.leave();
+    pub fn leave(&self) -> &Self {
+        self.last.unwrap()
     }
 }
 
-impl<K: Hash + Eq + Clone, V: Clone> LetEnv<K, V> {
-    pub fn new(map: Rc<HashMap<K, V>>) -> Self {
+impl<'bump, K: Hash + Eq + Clone, V: Clone> LetEnv<'bump, K, V> {
+    pub fn new(map: &'bump HashMap<K, V, DefaultHashBuilder, &Bump>) -> Self {
         Self {
             map: LetNode::Let(map),
             last: None,
@@ -122,45 +135,33 @@ impl<K: Hash + Eq + Clone, V: Clone> LetEnv<K, V> {
         self.last.as_ref().and_then(|env| env.lookup(symbol))
     }
 
-    pub fn enter_arg(self: &mut Rc<Self>, ident: K, val: V) {
-        let cloned = self.clone();
-        let mutref = Rc::make_mut(self);
-        mutref.last = Some(cloned);
-        mutref.map = LetNode::SingleArg(ident, val);
+    pub fn enter_arg(&'bump self, ident: K, val: V, bump: &'bump Bump) -> &'bump Self {
+        &*bump.alloc(Self {
+            map: LetNode::SingleArg(ident, val),
+            last: Some(self)
+        })
     }
 
-    pub fn enter_let(self: &mut Rc<Self>, map: Rc<HashMap<K, V>>) {
-        let cloned = self.clone();
-        let mutref = Rc::make_mut(self);
-        mutref.last = Some(cloned);
-        mutref.map = LetNode::Let(map);
-    }
-
-    pub fn leave(self: &mut Rc<Self>) {
-        let refmut = Rc::make_mut(self);
-        let last = refmut.last.take().unwrap();
-        *self = last;
+    pub fn enter_let(&'bump self, map: &'bump Map<'bump, K, V>, bump: &'bump Bump) -> &'bump Self {
+        &*bump.alloc(Self {
+            map: LetNode::Let(map),
+            last: Some(self)
+        })
     }
 }
 
-impl<K: Hash + Eq + Clone, V: Clone> With<K, V> {
-    pub fn lookup(&self, symbol: &K) -> Option<&V> {
+impl<'bump, K: Hash + Eq + Clone, V: Clone> With<'bump, K, V> {
+    pub fn lookup(&'bump self, symbol: &K) -> Option<&'bump V> {
         if let Some(val) = self.map.as_ref()?.get(symbol) {
             return Some(val);
         }
         self.last.as_ref().and_then(|env| env.lookup(symbol))
     }
 
-    pub fn enter(self: &mut Rc<Self>, map: Rc<HashMap<K, V>>) {
-        let cloned = self.clone();
-        let mutref = Rc::make_mut(self);
-        mutref.last = Some(cloned);
-        mutref.map = Some(map);
-    }
-
-    pub fn leave(self: &mut Rc<Self>) {
-        let refmut = Rc::make_mut(self);
-        let last = refmut.last.take().unwrap();
-        *self = last;
+    pub fn enter(&'bump self, map: &'bump Map<'bump, K, V>, bump: &'bump Bump) -> &'bump Self {
+        &*bump.alloc(Self {
+            map: Some(map),
+            last: Some(self)
+        })
     }
 }
diff --git a/src/vm/mod.rs b/src/vm/mod.rs
index 42b61d2..812b2c4 100644
--- a/src/vm/mod.rs
+++ b/src/vm/mod.rs
@@ -1,7 +1,7 @@
+use bumpalo::Bump;
 use hashbrown::{HashMap, HashSet};
 use inkwell::execution_engine::JitFunction;
 use std::cell::{Cell, OnceCell, RefCell};
-use std::rc::Rc;
 
 use crate::builtins::env;
 use crate::bytecode::{BinOp, Func as F, OpCode, OpCodes, Program, UnOp};
@@ -30,12 +30,13 @@ pub fn run(prog: Program, jit: JITContext<'_>) -> Result<p::Value> {
         symbols: RefCell::new(prog.symbols),
         symmap: RefCell::new(prog.symmap),
         consts: prog.consts,
+        bump: Bump::new(),
         jit,
     };
     let env = env(&vm);
     let mut seen = HashSet::new();
     let value = vm
-        .eval(prog.top_level.into_iter(), env.into())?
+        .eval(prog.top_level.into_iter(), vm.bump.alloc(env))?
         .to_public(&vm, &mut seen);
     Ok(value)
 }
@@ -47,6 +48,7 @@ pub struct VM<'jit> {
     symbols: RefCell<Vec<EcoString>>,
     symmap: RefCell<HashMap<EcoString, usize>>,
     consts: Box<[Const]>,
+    pub bump: Bump,
     jit: JITContext<'jit>,
 }
 
@@ -83,7 +85,7 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
     pub fn eval(
         &'vm self,
         opcodes: impl Iterator<Item = OpCode>,
-        mut env: Rc<VmEnv<'jit, 'vm>>,
+        mut env: &'vm VmEnv<'jit, 'vm>,
     ) -> Result<Value<'jit, 'vm>> {
         let mut stack = Stack::<_, STACK_SIZE>::new();
         let mut iter = opcodes.into_iter();
@@ -104,7 +106,7 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
         &'vm self,
         opcode: OpCode,
         stack: &'s mut Stack<Value<'jit, 'vm>, CAP>,
-        env: &mut Rc<VmEnv<'jit, 'vm>>,
+        env: &mut &'vm VmEnv<'jit, 'vm>,
     ) -> Result<usize> {
         match opcode {
             OpCode::Illegal => panic!("illegal opcode"),
@@ -112,7 +114,7 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
             OpCode::LoadThunk { idx } => {
                 stack.push(Value::Thunk(Thunk::new(self.get_thunk(idx)).into()))?
             }
-            OpCode::CaptureEnv => stack.tos().as_ref().unwrap_thunk().capture(env.clone()),
+            OpCode::CaptureEnv => stack.tos().as_ref().unwrap_thunk().capture(*env),
             OpCode::ForceValue => {
                 stack.tos_mut().force(self)?;
             }
@@ -131,7 +133,7 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
             OpCode::Func { idx } => {
                 let func = self.get_func(idx);
                 stack.push(Value::Func(
-                    Func::new(func, env.clone(), OnceCell::new(), Cell::new(0)).into(),
+                    Func::new(func, env, OnceCell::new(), Cell::new(0)).into(),
                 ))?;
             }
             OpCode::UnOp { op } => {
@@ -184,7 +186,8 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
                 stack.push(Value::AttrSet(AttrSet::with_capacity(cap).into()))?;
             }
             OpCode::FinalizeRec => {
-                env.enter_let(stack.tos().clone().unwrap_attr_set().into_inner());
+                let new = self.bump.alloc(HashMap::new_in(&self.bump));
+                *env = env.enter_let(stack.tos().as_ref().unwrap_attr_set().as_inner().iter().map(|(&k, v)| (k, v.clone())).collect_into(new), &self.bump);
                 stack.tos_mut().as_mut().unwrap_attr_set().capture(env);
             }
             OpCode::PushStaticAttr { name } => {
@@ -244,10 +247,16 @@ impl<'vm, 'jit: 'vm> VM<'jit> {
                         .clone(),
                 )?;
             }
-            OpCode::EnterLetEnv => env.enter_let(stack.pop().unwrap_attr_set().into_inner()),
-            OpCode::LeaveLetEnv => env.leave_let(),
-            OpCode::EnterWithEnv => env.enter_with(stack.pop().unwrap_attr_set().into_inner()),
-            OpCode::LeaveWithEnv => env.leave_with(),
+            OpCode::EnterLetEnv => {
+                let new = self.bump.alloc(HashMap::new_in(&self.bump));
+                *env = env.enter_let(stack.pop().unwrap_attr_set().into_inner().iter().map(|(&k, v)| (k, v.clone())).collect_into(new), &self.bump);
+            }
+            OpCode::LeaveLetEnv => *env = env.leave(),
+            OpCode::EnterWithEnv => {
+                let new = self.bump.alloc(HashMap::new_in(&self.bump));
+                *env = env.enter_with(stack.pop().unwrap_attr_set().into_inner().iter().map(|(&k, v)| (k, v.clone())).collect_into(new), &self.bump);
+            }
+            OpCode::LeaveWithEnv => *env = env.leave(),
             OpCode::Assert => {
                 if !stack.pop().unwrap_const().unwrap_bool() {
                     todo!()