diff --git a/aegisub/src/command/command.cpp b/aegisub/src/command/command.cpp
index 52b3ca532..86fce7993 100644
--- a/aegisub/src/command/command.cpp
+++ b/aegisub/src/command/command.cpp
@@ -34,7 +34,16 @@ namespace cmd {
 	}
 
 	void reg(Command *cmd) {
-		cmd_map[cmd->name()] = cmd;
+		std::string name = cmd->name();
+		if (cmd_map.count(name))
+			delete cmd_map[name];
+		cmd_map[name] = cmd;
+	}
+
+	void unreg(std::string const& name) {
+		iterator it = find_command(name);
+		delete it->second;
+		cmd_map.erase(it);
 	}
 
 	Command *get(std::string const& name) {
diff --git a/aegisub/src/command/command.h b/aegisub/src/command/command.h
index bc38e3f1e..71ee48bf6 100644
--- a/aegisub/src/command/command.h
+++ b/aegisub/src/command/command.h
@@ -137,9 +137,13 @@ namespace cmd {
 	void init_builtin_commands();
 
 	/// Register a command.
-	/// @param cmd Command object.
+	/// @param cmd Command object to register. The command system takes ownership of this object.
 	void reg(Command *cmd);
 
+	/// Unregister a command.
+	/// @param cmd Command name to unregister. The associated command object is deleted.
+	void unreg(std::string const& name);
+
 	/// Call a command.
 	/// @param name Name of the command to call.
 	/// @param c  Current Context.
@@ -149,6 +153,6 @@ namespace cmd {
 	/// @param Command object.
 	Command* get(std::string const& name);
 
-	/// Unregister all commands
+	/// Unregister and deletes all commands
 	void clear();
 } // namespace cmd