diff --git a/src/env.cpp b/src/env.cpp
index 5563d2ab4..6ba77a6e6 100644
--- a/src/env.cpp
+++ b/src/env.cpp
@@ -216,8 +216,10 @@ static const string_set_t env_electric = {L"history", L"pipestatus", L"status",
 
 static bool is_electric(const wcstring &key) { return contains(env_electric, key); }
 
-env_stack_t::env_stack_t() : vars_(make_unique<var_stack_t>()) {}
-env_stack_t::env_stack_t(std::unique_ptr<var_stack_t> vars) : vars_(std::move(vars)) {}
+env_scoped_t::env_scoped_t() : env_scoped_t(make_unique<var_stack_t>()) {}
+env_scoped_t::env_scoped_t(std::unique_ptr<var_stack_t> vars) : vars_(std::move(vars)) {}
+env_scoped_t::env_scoped_t(env_scoped_t &&) = default;
+env_scoped_t::~env_scoped_t() = default;
 
 void env_stack_t::universal_barrier() {
     ASSERT_IS_MAIN_THREAD();
@@ -233,9 +235,9 @@ void env_stack_t::universal_barrier() {
 }
 
 // Get the variable stack
-var_stack_t &env_stack_t::vars_stack() { return *vars_; }
+var_stack_t &env_scoped_t::vars_stack() { return *vars_; }
 
-const var_stack_t &env_stack_t::vars_stack() const { return *vars_; }
+const var_stack_t &env_scoped_t::vars_stack() const { return *vars_; }
 
 /// Return the current umask value.
 static mode_t get_umask() {
@@ -856,7 +858,7 @@ static maybe_t<env_var_t> get_electric(const wcstring &key, const environment_t
     DIE("unrecognized electric var name");
 }
 
-maybe_t<env_var_t> env_stack_t::get(const wcstring &key, env_mode_flags_t mode) const {
+maybe_t<env_var_t> env_scoped_t::get(const wcstring &key, env_mode_flags_t mode) const {
     const bool has_scope = mode & (ENV_LOCAL | ENV_GLOBAL | ENV_UNIVERSAL);
     const bool search_local = !has_scope || (mode & ENV_LOCAL);
     const bool search_global = !has_scope || (mode & ENV_GLOBAL);
@@ -953,7 +955,7 @@ static void add_key_to_string_set(const var_table_t &envs, std::set<wcstring> *s
     }
 }
 
-wcstring_list_t env_stack_t::get_names(int flags) const {
+wcstring_list_t env_scoped_t::get_names(int flags) const {
     scoped_lock locker(env_lock);
 
     wcstring_list_t result;
diff --git a/src/env.h b/src/env.h
index 9812077b3..fa598f629 100644
--- a/src/env.h
+++ b/src/env.h
@@ -193,13 +193,36 @@ class null_environment_t : public environment_t {
     wcstring_list_t get_names(int flags) const override;
 };
 
-/// A environment stack of scopes. This is the main class that tracks fish variables.
+/// An environment stack of scopes.
+/// The base implementation provides read-only access.
 struct var_stack_t;
 class env_node_t;
-class env_stack_t final : public environment_t {
-    friend class parser_t;
+class env_scoped_t : public environment_t {
+   private:
     std::unique_ptr<var_stack_t> vars_;
 
+   protected:
+    var_stack_t &vars_stack();
+    const var_stack_t &vars_stack() const;
+
+    explicit env_scoped_t(std::unique_ptr<var_stack_t> vars_);
+    env_scoped_t();
+    env_scoped_t(env_scoped_t &&);
+
+   public:
+    /// Gets the variable with the specified name, or none() if it does not exist.
+    maybe_t<env_var_t> get(const wcstring &key, env_mode_flags_t mode = ENV_DEFAULT) const override;
+
+    /// Returns all variable names.
+    wcstring_list_t get_names(int flags) const override;
+
+    ~env_scoped_t() override;
+};
+
+/// A mutable env_scoped_t, that allows scopes to be pushed and popped.
+class env_stack_t final : public env_scoped_t {
+    friend class parser_t;
+
     int set_internal(const wcstring &key, env_mode_flags_t var_mode, wcstring_list_t val);
 
     bool try_remove(std::shared_ptr<env_node_t> n, const wchar_t *key, int var_mode);
@@ -207,18 +230,11 @@ class env_stack_t final : public environment_t {
 
     static env_stack_t make_principal();
 
-    var_stack_t &vars_stack();
-    const var_stack_t &vars_stack() const;
-
-    explicit env_stack_t(std::unique_ptr<var_stack_t> vars_);
-    env_stack_t();
+    using env_scoped_t::env_scoped_t;
     ~env_stack_t() override;
-
     env_stack_t(env_stack_t &&);
 
    public:
-    /// Gets the variable with the specified name, or none() if it does not exist.
-    maybe_t<env_var_t> get(const wcstring &key, env_mode_flags_t mode = ENV_DEFAULT) const override;
 
     /// Sets the variable with the specified name to the given values.
     int set(const wcstring &key, env_mode_flags_t mode, wcstring_list_t vals);
@@ -254,9 +270,6 @@ class env_stack_t final : public environment_t {
     /// Returns an array containing all exported variables in a format suitable for execv
     const char *const *export_arr();
 
-    /// Returns all variable names.
-    wcstring_list_t get_names(int flags) const override;
-
     /// Update the termsize variable.
     void set_termsize();