diff --git a/src/ServerShell.cc b/src/ServerShell.cc
index ea4d327f..fd31f9d4 100644
--- a/src/ServerShell.cc
+++ b/src/ServerShell.cc
@@ -17,7 +17,7 @@ using namespace std;
 
 struct CommandArgs {
   shared_ptr<ServerState> s;
-  shared_ptr<ServerShell> shell;
+  ServerShell* shell;
   string command;
   string args;
   string session_name;
@@ -107,17 +107,10 @@ void ServerShell::thread_fn() {
     }
 
     phosg::strip_trailing_whitespace(command);
+    phosg::strip_leading_whitespace(command);
 
     try {
-      // Find the entry in the command table and run the command
-      size_t command_end = phosg::skip_non_whitespace(command, 0);
-      size_t args_begin = phosg::skip_whitespace(command, command_end);
-      CommandArgs args;
-      args.s = this->state;
-      args.shell = this->shared_from_this();
-      args.command = command.substr(0, command_end);
-      args.args = command.substr(args_begin);
-      CommandDefinition::dispatch(args);
+      this->execute_command(command);
     } catch (const exit_shell&) {
       event_base_loopexit(this->state->base.get(), nullptr);
       return;
@@ -127,6 +120,18 @@ void ServerShell::thread_fn() {
   }
 }
 
+void ServerShell::execute_command(const string& command) {
+  // Find the entry in the command table and run the command
+  size_t command_end = phosg::skip_non_whitespace(command, 0);
+  size_t args_begin = phosg::skip_whitespace(command, command_end);
+  CommandArgs args;
+  args.s = this->state;
+  args.shell = this;
+  args.command = command.substr(0, command_end);
+  args.args = command.substr(args_begin);
+  CommandDefinition::dispatch(args);
+}
+
 shared_ptr<ProxyServer::LinkedSession> ServerShell::get_proxy_session(const string& name) {
   if (!this->state->proxy_server.get()) {
     throw runtime_error("the proxy server is disabled");
diff --git a/src/ServerShell.hh b/src/ServerShell.hh
index 457ceda0..dd57d045 100644
--- a/src/ServerShell.hh
+++ b/src/ServerShell.hh
@@ -25,6 +25,8 @@ public:
 
   std::shared_ptr<ProxyServer::LinkedSession> get_proxy_session(const std::string& name);
 
+  void execute_command(const std::string& command);
+
 protected:
   std::shared_ptr<ServerState> state;
   std::thread th;
diff --git a/src/ServerState.hh b/src/ServerState.hh
index 11238adf..cca04e6b 100644
--- a/src/ServerState.hh
+++ b/src/ServerState.hh
@@ -383,7 +383,7 @@ struct ServerState : public std::enable_shared_from_this<ServerState> {
   std::vector<PortConfiguration> parse_port_configuration(const phosg::JSON& json) const;
 
   template <typename T>
-  inline void call_on_event_thread(std::function<T()>&& fn) {
+  inline T call_on_event_thread(std::function<T()>&& fn) {
     return ::call_on_event_thread<T>(this->base, std::move(fn));
   }
   inline void forward_to_event_thread(std::function<void()>&& fn) {