diff --git a/src/obj/attrs.rs b/src/obj/attrs.rs
index f912ed8..ca9af28 100644
--- a/src/obj/attrs.rs
+++ b/src/obj/attrs.rs
@@ -1,11 +1,11 @@
 use crate::obj::{sym::Sym, ObjRef};
 use shredder::{Gc, Scan};
 use std::{
-    collections::BTreeMap,
+    collections::HashMap,
     ops::{Deref, DerefMut},
 };
 
-pub type Attrs = BTreeMap<Sym, ObjRef>;
+pub type Attrs = HashMap<Sym, ObjRef>;
 pub type VtableAttrs = Gc<Attrs>;
 
 #[derive(Scan, Debug, Clone, Default)]
diff --git a/src/obj/builtin.rs b/src/obj/builtin.rs
index 5a4edc2..129bed5 100644
--- a/src/obj/builtin.rs
+++ b/src/obj/builtin.rs
@@ -4,9 +4,9 @@ use crate::{
     obj::{prelude::*, reserved::*},
     vm::{error::*, signal::*},
 };
-use maplit::btreemap;
+use maplit::hashmap;
 use once_cell::sync::Lazy;
-use std::collections::BTreeMap;
+use std::collections::HashMap;
 
 ////////////////////////////////////////////////////////////////////////////////
 // Builtin free functions
@@ -74,8 +74,8 @@ pub static PRINT_BUILTIN_FUN: Lazy<NativeFunRef> = Lazy::new(|| {
 // Builtin objects
 ////////////////////////////////////////////////////////////////////////////////
 
-pub static BUILTIN_OBJS: Lazy<BTreeMap<Sym, ObjRef>> = Lazy::new(|| {
-    btreemap! {
+pub static BUILTIN_OBJS: Lazy<HashMap<Sym, ObjRef>> = Lazy::new(|| {
+    hashmap! {
         PRINTLN_BUILTIN_NAME.sym => PRINTLN_BUILTIN_FUN.clone() as _,
         PRINT_BUILTIN_NAME.sym => PRINT_BUILTIN_FUN.clone() as _,
     }
diff --git a/src/obj/fun.rs b/src/obj/fun.rs
index cd3be7a..eeefd51 100644
--- a/src/obj/fun.rs
+++ b/src/obj/fun.rs
@@ -121,6 +121,7 @@ impl UserFun {
         &self.locals
     }
 
+    /// Dump this function's code to the given writer.
     pub fn dump(
         &self,
         writer: &mut dyn Write,
diff --git a/src/obj/macros.rs b/src/obj/macros.rs
index 88177fe..2718d88 100644
--- a/src/obj/macros.rs
+++ b/src/obj/macros.rs
@@ -86,22 +86,22 @@ macro_rules! read_obj_downcast {
 #[macro_export]
 macro_rules! attrs {
     ($($key:expr => $value:expr),+ $(,)?) => {{
-        maplit::btreemap! { $($key => ($value as _) ),+ }
+        maplit::hashmap! { $($key => ($value as _) ),+ }
     }};
 
     () => {{
-        maplit::btreemap! { }
+        maplit::hashmap! { }
     }}
 }
 
 #[macro_export]
 macro_rules! vtable {
     ($($key:expr => $value:expr),+ $(,)?) => {{
-        $crate::obj::attrs::Vtable::new(maplit::btreemap! { $($key => ($value as _) ),+ })
+        $crate::obj::attrs::Vtable::new(maplit::hashmap! { $($key => ($value as _) ),+ })
     }};
 
     () => {{
-        $crate::obj::attrs::Vtable::new(maplit::btreemap! { })
+        $crate::obj::attrs::Vtable::new(maplit::hashmap! { })
     }}
 }
 
diff --git a/src/obj/sym.rs b/src/obj/sym.rs
index b5f1855..d79a7bb 100644
--- a/src/obj/sym.rs
+++ b/src/obj/sym.rs
@@ -1,7 +1,7 @@
 use crate::obj::{intern::Interner, prelude::*, reserved::*};
 use once_cell::sync::Lazy;
 use std::{
-    collections::BTreeMap,
+    collections::HashMap,
     sync::{Arc, Mutex},
 };
 
@@ -69,7 +69,7 @@ pub static SYM_VTABLE: Lazy<Vtable> = Lazy::new(|| vtable! {});
 //
 // global interned symbol obj table
 //
-pub(crate) static SYM_REFS: Lazy<Mutex<BTreeMap<Sym, SymRef>>> = Lazy::new(|| Default::default());
+pub(crate) static SYM_REFS: Lazy<Mutex<HashMap<Sym, SymRef>>> = Lazy::new(|| Default::default());
 
 /// Access or insert a globally interned symbol object.
 ///
diff --git a/src/vm/frame.rs b/src/vm/frame.rs
index 4f55b4f..4cc9830 100644
--- a/src/vm/frame.rs
+++ b/src/vm/frame.rs
@@ -1,8 +1,8 @@
 use crate::{obj::prelude::*, vm::inst::Inst};
 use std::fmt::{self, Debug, Formatter};
-use std::{collections::BTreeMap, sync::Arc};
+use std::{collections::HashMap, sync::Arc};
 
-pub type FrameBindings = BTreeMap<usize, ObjRef>;
+pub type FrameBindings = HashMap<usize, ObjRef>;
 
 #[derive(Debug)]
 pub enum Frame {