diff --git a/single_ursim_control/plugin_repository.py b/single_ursim_control/plugin_repository.py
index 2771bb5..b1379a5 100644
--- a/single_ursim_control/plugin_repository.py
+++ b/single_ursim_control/plugin_repository.py
@@ -11,6 +11,10 @@ class UnknownPlugin(Exception):
     pass
 
 
+class UnknownCommand(Exception):
+    pass
+
+
 class PluginRepository:
 
     def __init__(self):
@@ -67,7 +71,10 @@ class PluginRepository:
         return list(self._command_compilers.keys())
 
     def get_compiler(self, command: str) -> AbstractCommandCompiler:
-        return self._command_compilers[command]
+        try:
+            return self._command_compilers[command]
+        except KeyError:
+            raise UnknownCommand(f"Could not find compiler for command: {command}! A plugin might be not loaded.")
 
     def get_plugin_instance(self, plugin: str) -> AbstractPlugin:
         return self._loaded_plugins[plugin]