diff --git a/src/arena.hpp b/src/arena.hpp
index 0514aba..db057f0 100644
--- a/src/arena.hpp
+++ b/src/arena.hpp
@@ -39,7 +39,7 @@ class GcRoot : public GcRootBase {
   GcRoot& operator=(GcRoot&& rhs);
 
   static Result<GcRoot<T>> create(T* ptr, Arena& arena);
-  Result<GcRoot<T>> copy(Arena& arena) {
+  Result<GcRoot<T>> copy(Arena& arena) const {
     return GcRoot<T>::create((T*)_ptr, arena);
   }
 
diff --git a/src/common.cpp b/src/common.cpp
index e66d1d8..e095795 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -78,44 +78,44 @@ Result<Value> syntax_unwrap(Arena& arena, Value& val) {
   return syntax->get_value(arena);
 }
 
-Result<Value> Nil::copy(Arena& arena) { return Value(Nil()); }
+Result<Value> Nil::copy(Arena& arena) const { return Value(Nil()); }
 
-Result<Value> Int64::copy(Arena& arena) {
+Result<Value> Int64::copy(Arena& arena) const {
   return Value(Int64(TRY(_value.copy(arena))));
 }
-Result<Value> Float::copy(Arena& arena) {
+Result<Value> Float::copy(Arena& arena) const {
   return Value(Float(TRY(_value.copy(arena))));
 }
 
-Result<Value> Array::copy(Arena& arena) {
+Result<Value> Array::copy(Arena& arena) const {
   return Value(Array(TRY(_value.copy(arena))));
 }
 
-Result<Value> ByteArray::copy(Arena& arena) {
+Result<Value> ByteArray::copy(Arena& arena) const {
   return Value(ByteArray(TRY(_value.copy(arena))));
 }
 
-Result<Value> Dict::copy(Arena& arena) {
+Result<Value> Dict::copy(Arena& arena) const {
   return Value(Dict(TRY(_value.copy(arena))));
 }
 
-Result<Value> String::copy(Arena& arena) {
+Result<Value> String::copy(Arena& arena) const {
   return Value(String(TRY(_value.copy(arena))));
 }
 
-Result<Value> Symbol::copy(Arena& arena) {
+Result<Value> Symbol::copy(Arena& arena) const {
   return Value(Symbol(TRY(_value.copy(arena))));
 }
 
-Result<Value> Syntax::copy(Arena& arena) {
+Result<Value> Syntax::copy(Arena& arena) const {
   return Value(Syntax(TRY(_value.copy(arena))));
 }
 
-Result<Value> Pair::copy(Arena& arena) {
+Result<Value> Pair::copy(Arena& arena) const {
   return Value(Pair(TRY(_value.copy(arena))));
 }
 
-Result<Value> Bool::copy(Arena& arena) {
+Result<Value> Bool::copy(Arena& arena) const {
   return Value(Bool(TRY(_value.copy(arena))));
 }
 
@@ -176,6 +176,11 @@ Result<Value> Array::get(Arena& arena, uint64_t idx) {
   return Value::create(arena, val);
 }
 
+Result<Value> Array::get(Arena& arena, Value& key) {
+  if (!key.is<Int64>()) return ErrorCode::TypeMismatch;
+  return get(arena, key.to<Int64>()->value());
+}
+
 Result<Array> Array::append(Arena& arena, Value& rhs) {
   uint64_t res_size = size() + 1;
 
@@ -293,3 +298,7 @@ Result<short> Dict::cmp(Arena& arena, Dict& rhs) {
   }
   return 0;
 }
+
+Result<Value> Object::get(Arena& arena, Value& key) {
+  return ErrorCode::TypeMismatch;
+}
diff --git a/src/common.hpp b/src/common.hpp
index b456fb5..9eeef78 100644
--- a/src/common.hpp
+++ b/src/common.hpp
@@ -6,6 +6,7 @@
 #include <iostream>
 
 #include "arena.hpp"
+#include "error.hpp"
 #include "pod.hpp"
 #include "utf8.hpp"
 
@@ -30,7 +31,7 @@ short cmp_tag(Tag lhs, Tag rhs);
 class Object {
  public:
   virtual Tag tag() = 0;
-  virtual Result<Value> copy(Arena& arena) = 0;
+  virtual Result<Value> copy(Arena& arena) const = 0;
   virtual PodObject* pod() = 0;
   virtual void move(Object*) = 0;
   virtual ~Object() = default;
@@ -60,6 +61,7 @@ class Object {
   virtual Result<short> cmp(Arena&, ByteArray&) {
     return cmp_tag(tag(), Tag::ByteArray);
   }
+  virtual Result<Value> get(Arena& arena, Value& key);
 
   Object() = default;
   Object(const Object&) = delete;
@@ -90,7 +92,7 @@ class Nil : public Object {
     return Nil(TRY(MkGcRoot(pod, arena)));
   }
 
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
   virtual void move(Object* obj) final { new (obj) Nil(std::move(_value)); }
 
@@ -132,9 +134,10 @@ class Array : public Object {
   }
 
   uint64_t size() { return _value->size; }
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
   Result<Value> get(Arena& arena, uint64_t idx);
+  virtual Result<Value> get(Arena& arena, Value& key) final;
 
   Result<Array> append(Arena& arena, Value& rhs);
 
@@ -214,7 +217,7 @@ class ByteArray : public Object {
   static Result<ByteArray> create(Arena& arena, String& str);
 
   uint64_t size() { return _value->size; }
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
   Result<char> operator[](uint64_t idx) {
     if (idx >= _value->size) return ErrorCode::IndexOutOfRange;
@@ -307,9 +310,9 @@ class Dict : public Object {
     return Dict(TRY(MkGcRoot(pod, arena)));
   }
 
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
-  Result<Value> get(Arena& arena, Value& key);
+  virtual Result<Value> get(Arena& arena, Value& key) final;
 
   Result<Dict> insert(Arena& arena, Value& key, Value& value);
 
@@ -400,7 +403,7 @@ class String : public Object {
   }
 
   uint64_t size() { return _value->size; }
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
   Result<char32_t> operator[](uint64_t idx) {
     if (idx >= _value->size) return ErrorCode::IndexOutOfRange;
@@ -493,7 +496,7 @@ class Symbol : public Object {
   }
 
   static Result<Symbol> create(Arena& arena, String& rhs);
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
   uint64_t size() { return _value->size; }
 
@@ -527,7 +530,7 @@ class Syntax : public Object {
 
   Result<Value> get_value(Arena& arena);
 
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
  private:
   GcRoot<PodSyntax> _value;
@@ -555,7 +558,7 @@ class Pair : public Object {
   Result<Value> first(Arena& arena);
   Result<Value> rest(Arena& arena);
 
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
  private:
   GcRoot<PodPair> _value;
@@ -595,7 +598,7 @@ class Int64 : public Object {
 
   int64_t value() { return _value->value; }
 
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
  private:
   GcRoot<PodInt64> _value;
@@ -635,7 +638,7 @@ class Float : public Object {
 
   double value() { return _value->value; }
 
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
  private:
   GcRoot<PodFloat> _value;
@@ -670,7 +673,7 @@ class Bool : public Object {
 
   bool value() { return _value->value; }
 
-  virtual Result<Value> copy(Arena& arena) final;
+  virtual Result<Value> copy(Arena& arena) const final;
 
  private:
   GcRoot<PodBool> _value;
@@ -731,11 +734,19 @@ class Value {
     return ((Object*)buf)->cmp(arena, *(Object*)rhs.buf);
   }
 
+  Result<Value> get(Arena& arena, Value& key) {
+    return ((Object*)buf)->get(arena, key);
+  }
+  Result<Value> get(Arena& arena, int64_t key) {
+    Value k = TRY(Int64::create(arena, key));
+    return ((Object*)buf)->get(arena, k);
+  }
+
   // TODO: cmp() probably doesn't need arena parameter
   // Result<bool> operator==(Value& rhs) { return TRY(cmp(rhs)) == 0; }
   // Result<bool> operator!=(Value& rhs) { return TRY(cmp(rhs)) != 0; }
 
-  Result<Value> copy(Arena& arena) { return ((Object*)buf)->copy(arena); }
+  Result<Value> copy(Arena& arena) const { return ((Object*)buf)->copy(arena); }
 
  private:
   uint8_t buf[24];
diff --git a/test/dict.cpp b/test/dict.cpp
index 1dac3dc..48b6e17 100644
--- a/test/dict.cpp
+++ b/test/dict.cpp
@@ -33,4 +33,7 @@ TEST_CASE(dict_read) {
   v = DIEX(read_one(arena, "{1 2 3 4}"));
   s = DIEX(write_one(arena, v));
   ASSERT_EQUALS(s, "{1 2 3 4}");
+
+  auto vv = DIEX(v.get(arena, 1));
+  ASSERT_EQUALS(vv, 2);
 }
diff --git a/test/test.hpp b/test/test.hpp
index f738f7c..4c0d9f2 100644
--- a/test/test.hpp
+++ b/test/test.hpp
@@ -3,6 +3,7 @@
 #include <algorithm>
 #include <cstdint>
 #include <cstdio>
+#include <type_traits>
 
 #include "common.hpp"
 #include "result.hpp"
@@ -42,44 +43,33 @@ bool run_tests() {
 
 #define TEST_CASE(fun_) TEST_CASE_IMPL(MACRO_CONCAT(fun_, _COUNTER_))
 
-template <class T>
-struct Capture {
-  Capture(T& value) : value(value) {}
-  T& value;
-};
-
-template <class T>
-struct Capture<T&> {
-  Capture(T& value) : value(value) {}
-  T& value;
-};
-
-template <class T>
-struct Capture<T&&> {
-  Capture(T&& value) : value(value) {}
-  T value;
-};
-
-Value& to_value(Arena& arena, Value& val) { return val; }
-
-template <class T>
-  requires std::derived_from<T, Object>
-Value to_value(Arena& arena, T& val) {
-  return DIEX(val.copy(arena));
+Result<Value> to_value(Arena& arena, Value& val) { return val.copy(arena); }
+Result<Value> to_value(Arena& arena, const Value& val) {
+  return val.copy(arena);
 }
 
 template <class T>
-  requires(!std::derived_from<T, Object>)
-Value to_value(Arena& arena, T& val) {
-  return DIEX(Value::create(arena, val));
+  requires std::derived_from<T, Object>
+Result<Value> to_value(Arena& arena, T& val) {
+  return val.copy(arena);
+}
+
+template <class T>
+  requires(!std::derived_from<T, Object> && !std::is_fundamental<T>::value)
+Result<Value> to_value(Arena& arena, T& val) {
+  return Value::create(arena, val);
+}
+
+template <class T>
+  requires(!std::derived_from<T, Object> && std::is_fundamental<T>::value)
+Result<Value> to_value(Arena& arena, T val) {
+  return Value::create(arena, val);
 }
 
 #define ASSERT_EQUALS(lhs, rhs)                                           \
   do {                                                                    \
-    auto l = Capture(lhs);                                                \
-    auto r = Capture(rhs);                                                \
-    auto lv = to_value(arena, l.value);                                   \
-    auto rv = to_value(arena, r.value);                                   \
+    auto lv = DIEX(to_value(arena, lhs));                                 \
+    auto rv = DIEX(to_value(arena, rhs));                                 \
     short c = DIEX(lv.cmp(arena, rv));                                    \
     if (c != 0) {                                                         \
       fprintf(stderr, "Values not equal at %s:%d\n", __FILE__, __LINE__); \