diff --git a/src/nix/command.cc b/src/nix/command.cc
index 724f03e5d..a40a113db 100644
--- a/src/nix/command.cc
+++ b/src/nix/command.cc
@@ -5,7 +5,7 @@
 
 namespace nix {
 
-Commands * RegisterCommand::commands = 0;
+std::vector<ref<Command>> * RegisterCommand::commands = 0;
 
 void Command::printHelp(const string & programName, std::ostream & out)
 {
@@ -22,9 +22,11 @@ void Command::printHelp(const string & programName, std::ostream & out)
     }
 }
 
-MultiCommand::MultiCommand(const Commands & _commands)
-    : commands(_commands)
+MultiCommand::MultiCommand(const std::vector<ref<Command>> & _commands)
 {
+    for (auto & command : _commands)
+        commands.emplace(command->name(), command);
+
     expectedArgs.push_back(ExpectedArg{"command", 1, true, [=](std::vector<std::string> ss) {
         assert(!command);
         auto i = commands.find(ss[0]);
diff --git a/src/nix/command.hh b/src/nix/command.hh
index 2db22dba2..be56f8992 100644
--- a/src/nix/command.hh
+++ b/src/nix/command.hh
@@ -182,7 +182,7 @@ public:
 
     std::shared_ptr<Command> command;
 
-    MultiCommand(const Commands & commands);
+    MultiCommand(const std::vector<ref<Command>> & commands);
 
     void printHelp(const string & programName, std::ostream & out) override;
 
@@ -194,12 +194,12 @@ public:
 /* A helper class for registering commands globally. */
 struct RegisterCommand
 {
-    static Commands * commands;
+    static std::vector<ref<Command>> * commands;
 
     RegisterCommand(ref<Command> command)
     {
-        if (!commands) commands = new Commands;
-        commands->emplace(command->name(), command);
+        if (!commands) commands = new std::vector<ref<Command>>;
+        commands->push_back(command);
     }
 };
 
diff --git a/src/nix/main.cc b/src/nix/main.cc
index 1c9d909d8..d5cba7fb9 100644
--- a/src/nix/main.cc
+++ b/src/nix/main.cc
@@ -104,10 +104,15 @@ struct NixArgs : virtual MultiCommand, virtual MixCommonArgs
             "--help-config' for a list of configuration settings.\n";
     }
 
+    void printHelp(const string & programName, std::ostream & out)
+    {
+        MultiCommand::printHelp(programName, out);
+        std::cout << "\nNote: this program is EXPERIMENTAL and subject to change.\n";
+    }
+
     void showHelpAndExit()
     {
         printHelp(programName, std::cout);
-        std::cout << "\nNote: this program is EXPERIMENTAL and subject to change.\n";
         throw Exit();
     }
 };