diff --git a/server/message_parser.cpp b/server/message_parser.cpp
index d660ab6..fd2f101 100644
--- a/server/message_parser.cpp
+++ b/server/message_parser.cpp
@@ -32,12 +32,22 @@ json Simulators::command_parser(json command)
         {
         case Command::get_UI_element:
             SPDLOG_INFO("Command {}: {}", type, (size_t)command.at("id"));
+            if (is_not_active())
+            {
+                SPDLOG_ERROR("Command got called but there is no active simulator");
+                return j;
+            }
             j["response"]["type"] = type;
             j["response"]["UI_item"] =
                 invoke_active_simulator()->get_UI_item(command.at("id"))->to_json(command.at("id"));
             break;
         case Command::get_UI_elements:
             SPDLOG_INFO("Command {}", type);
+            if (is_not_active())
+            {
+                SPDLOG_ERROR("Command got called but there is no active simulator");
+                return j;
+            }
             j["response"]["type"] = type;
             j["response"]["UI_items"] = invoke_active_simulator()->get_UI_items()["UI_items"];
             break;
diff --git a/server/simulators.cpp b/server/simulators.cpp
index 2c9f6f9..3b4add8 100644
--- a/server/simulators.cpp
+++ b/server/simulators.cpp
@@ -151,6 +151,11 @@ std::vector<std::string> Simulators::list_simulators() const
     return names;
 }
 
+bool Simulators::is_not_active() const
+{
+    return this->m_current_simulator.empty();
+}
+
 Simulator_base *Simulators::invoke_active_simulator()
 {
     std::lock_guard<std::mutex> lock(m_mutex);
diff --git a/server/simulators.hpp b/server/simulators.hpp
index 00b5a9e..f103806 100644
--- a/server/simulators.hpp
+++ b/server/simulators.hpp
@@ -52,6 +52,7 @@ class Simulators : public QObject
     void stop();
     void switch_simulator(std::string name);
     std::vector<std::string> list_simulators() const;
+    bool is_not_active() const;
     Simulator_base *invoke_active_simulator();
     json changed_UI_items();