diff --git a/src/env_vars.cc b/src/env_vars.cc
index 1d52df93..0e5c53e8 100644
--- a/src/env_vars.cc
+++ b/src/env_vars.cc
@@ -16,7 +16,7 @@ EnvVarMap get_env_vars()
         const char* value = name;
         while (*value != 0 and *value != '=')
             ++value;
-        env_vars[{name, value}] = (*value == '=') ? value+1 : String{};
+        env_vars.append({{name, value}, (*value == '=') ? value+1 : String{}});
     }
     return env_vars;
 }
diff --git a/src/env_vars.hh b/src/env_vars.hh
index 43bbe2de..7445c216 100644
--- a/src/env_vars.hh
+++ b/src/env_vars.hh
@@ -1,13 +1,13 @@
 #ifndef env_vars_hh_INCLUDED
 #define env_vars_hh_INCLUDED
 
-#include "unordered_map.hh"
+#include "id_map.hh"
 
 namespace Kakoune
 {
 
 class String;
-using EnvVarMap = UnorderedMap<String, String, MemoryDomain::EnvVars>;
+using EnvVarMap = IdMap<String, MemoryDomain::EnvVars>;
 
 EnvVarMap get_env_vars();
 
diff --git a/src/id_map.hh b/src/id_map.hh
index 72d1c2f0..9b6f553b 100644
--- a/src/id_map.hh
+++ b/src/id_map.hh
@@ -69,11 +69,29 @@ public:
         return (m_content.end()-1)->second;
     }
 
-    const Value& operator[](StringView id) const
+    template<MemoryDomain dom>
+    bool operator==(const IdMap<Value, dom>& other) const
     {
-        return (*const_cast<IdMap*>(this))[id];
+        if (size() != other.size())
+            return false;
+        for (size_t i = 0, s = size(); i < s; ++i)
+        {
+            if (m_content[i] != other.m_content[i])
+                return false;
+        }
+        return true;
     }
 
+    template<MemoryDomain dom>
+    bool operator!=(const IdMap<Value, dom>& other) const
+    {
+        return not (*this == other);
+    }
+
+    void reserve(size_t size) { m_content.reserve(size); }
+    size_t size() const { return m_content.size(); }
+    void clear() { m_content.clear(); }
+
     static const String& get_id(const value_type& v) { return v.first; }
 
     bool empty() const { return m_content.empty(); }
diff --git a/src/option_types.hh b/src/option_types.hh
index a4d29227..d04544dd 100644
--- a/src/option_types.hh
+++ b/src/option_types.hh
@@ -6,7 +6,7 @@
 #include "units.hh"
 #include "coord.hh"
 #include "array_view.hh"
-#include "unordered_map.hh"
+#include "id_map.hh"
 
 #include <tuple>
 #include <vector>
@@ -67,8 +67,8 @@ bool option_add(Vector<T, domain>& opt, const Vector<T, domain>& vec)
     return not vec.empty();
 }
 
-template<typename Key, typename Value, MemoryDomain domain>
-String option_to_string(const UnorderedMap<Key, Value, domain>& opt)
+template<typename Value, MemoryDomain domain>
+String option_to_string(const IdMap<Value, domain>& opt)
 {
     String res;
     for (auto it = begin(opt); it != end(opt); ++it)
@@ -82,8 +82,8 @@ String option_to_string(const UnorderedMap<Key, Value, domain>& opt)
     return res;
 }
 
-template<typename Key, typename Value, MemoryDomain domain>
-void option_from_string(StringView str, UnorderedMap<Key, Value, domain>& opt)
+template<typename Value, MemoryDomain domain>
+void option_from_string(StringView str, IdMap<Value, domain>& opt)
 {
     opt.clear();
     for (auto& elem : split(str, list_separator, '\\'))
@@ -91,10 +91,11 @@ void option_from_string(StringView str, UnorderedMap<Key, Value, domain>& opt)
         Vector<String> pair_str = split(elem, '=', '\\');
         if (pair_str.size() != 2)
             throw runtime_error("map option expects key=value");
-        std::pair<Key, Value> pair;
-        option_from_string(pair_str[0], pair.first);
-        option_from_string(pair_str[1], pair.second);
-        opt.insert(std::move(pair));
+        String key;
+        Value value;
+        option_from_string(pair_str[0], key);
+        option_from_string(pair_str[1], value);
+        opt.append({ std::move(key), std::move(value) });
     }
 }
 
diff --git a/src/remote.cc b/src/remote.cc
index 1c8795d3..d22ee6f8 100644
--- a/src/remote.cc
+++ b/src/remote.cc
@@ -7,6 +7,7 @@
 #include "display_buffer.hh"
 #include "event_manager.hh"
 #include "file.hh"
+#include "id_map.hh"
 
 #include <sys/types.h>
 #include <sys/socket.h>
@@ -84,8 +85,8 @@ public:
         write(ConstArrayView<T>(vec));
     }
 
-    template<typename Key, typename Val, MemoryDomain domain>
-    void write(const UnorderedMap<Key, Val, domain>& map)
+    template<typename Val, MemoryDomain domain>
+    void write(const IdMap<Val, domain>& map)
     {
         write<uint32_t>(map.size());
         for (auto& val : map)
@@ -215,16 +216,17 @@ DisplayBuffer read<DisplayBuffer>(int socket)
     return db;
 }
 
-template<typename Key, typename Val, MemoryDomain domain>
-UnorderedMap<Key, Val, domain> read_map(int socket)
+template<typename Val, MemoryDomain domain>
+IdMap<Val, domain> read_idmap(int socket)
 {
     uint32_t size = read<uint32_t>(socket);
-    UnorderedMap<Key, Val, domain> res;
+    IdMap<Val, domain> res;
+    res.reserve(size);
     while (size--)
     {
-        auto key = read<Key>(socket);
+        auto key = read<String>(socket);
         auto val = read<Val>(socket);
-        res.insert({std::move(key), std::move(val)});
+        res.append({std::move(key), std::move(val)});
     }
     return res;
 }
@@ -512,7 +514,7 @@ void RemoteClient::process_next_message()
         m_ui->refresh();
         break;
     case RemoteUIMsg::SetOptions:
-        m_ui->set_ui_options(read_map<String, String, MemoryDomain::Options>(socket));
+        m_ui->set_ui_options(read_idmap<String, MemoryDomain::Options>(socket));
         break;
     }
 }
@@ -579,7 +581,7 @@ private:
             }
             if (c == 0) // end of initial command stream, go to interactive ui
             {
-                EnvVarMap env_vars = read_map<String, String, MemoryDomain::EnvVars>(socket);
+                EnvVarMap env_vars = read_idmap<String, MemoryDomain::EnvVars>(socket);
                 std::unique_ptr<UserInterface> ui{new RemoteUI{socket}};
                 ClientManager::instance().create_client(std::move(ui),
                                                         std::move(env_vars),
diff --git a/src/shell_manager.cc b/src/shell_manager.cc
index 19d55bb3..1e29ba2d 100644
--- a/src/shell_manager.cc
+++ b/src/shell_manager.cc
@@ -109,7 +109,7 @@ std::pair<String, int> ShellManager::eval(
             StringView name{match[1].first, match[1].second};
             kak_assert(name.length() > 0);
 
-            auto local_var = env_vars.find(name.str());
+            auto local_var = env_vars.find(name);
             if (local_var != env_vars.end())
                 setenv(("kak_" + name).c_str(), local_var->second.c_str(), 1);
             else try
diff --git a/src/user_interface.hh b/src/user_interface.hh
index 5f87d58b..daae4f9d 100644
--- a/src/user_interface.hh
+++ b/src/user_interface.hh
@@ -3,7 +3,7 @@
 
 #include "array_view.hh"
 #include "safe_ptr.hh"
-#include "unordered_map.hh"
+#include "id_map.hh"
 
 #include <functional>
 
@@ -67,7 +67,7 @@ public:
 
     virtual void set_input_callback(InputCallback callback) = 0;
 
-    using Options = UnorderedMap<String, String, MemoryDomain::Options>;
+    using Options = IdMap<String, MemoryDomain::Options>;
     virtual void set_ui_options(const Options& options) = 0;
 };