diff --git a/OpenRA.Mods.RA/Scripting/LuaScriptContext.cs b/OpenRA.Mods.RA/Scripting/LuaScriptContext.cs
index 564cfdf575..12a44ff2e0 100644
--- a/OpenRA.Mods.RA/Scripting/LuaScriptContext.cs
+++ b/OpenRA.Mods.RA/Scripting/LuaScriptContext.cs
@@ -13,6 +13,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
 using NLua;
+using NLua.Event;
 using OpenRA.FileFormats;
 
 namespace OpenRA.Mods.RA.Scripting
@@ -26,6 +27,7 @@ namespace OpenRA.Mods.RA.Scripting
 		{
 			Log.Write("debug", "Creating Lua script context");
 			Lua = new Lua();
+			Lua.HookException += OnLuaException;
 			functionCache = new Cache<string, LuaFunction>(Lua.GetFunction);
 		}
 
@@ -79,11 +81,21 @@ namespace OpenRA.Mods.RA.Scripting
 			}
 		}
 
-		void LogException(Exception e)
+		void OnLuaException(object sender, HookExceptionEventArgs e)
 		{
-			Game.Debug("{0}", e.Message);
+			ShowException(e.Exception);
+		}
+
+		void ShowException(Exception e)
+		{
+			ShowErrorMessage(e.Message, e.ToString());
+		}
+
+		public void ShowErrorMessage(string shortMessage, string longMessage)
+		{
+			Game.Debug("{0}", shortMessage);
 			Game.Debug("See debug.log for details");
-			Log.Write("debug", "{0}", e);
+			Log.Write("debug", "{0}", longMessage ?? shortMessage);
 		}
 
 		public void LoadLuaScripts(Func<string, string> getFileContents, params string[] files)
@@ -98,7 +110,7 @@ namespace OpenRA.Mods.RA.Scripting
 				}
 				catch (Exception e)
 				{
-					LogException(e);
+					ShowException(e);
 				}
 			}
 		}
@@ -114,7 +126,7 @@ namespace OpenRA.Mods.RA.Scripting
 			}
 			catch (Exception e)
 			{
-				LogException(e);
+				ShowException(e);
 				return null;
 			}
 		}
diff --git a/OpenRA.Mods.RA/Scripting/LuaScriptInterface.cs b/OpenRA.Mods.RA/Scripting/LuaScriptInterface.cs
index 4ee29f8ffa..0bd4844f83 100644
--- a/OpenRA.Mods.RA/Scripting/LuaScriptInterface.cs
+++ b/OpenRA.Mods.RA/Scripting/LuaScriptInterface.cs
@@ -43,7 +43,7 @@ namespace OpenRA.Mods.RA.Scripting
 		public void WorldLoaded(World w, WorldRenderer wr)
 		{
 			world = w;
-			AddMapActorGlobals();
+
 			context.Lua["World"] = w;
 			context.Lua["WorldRenderer"] = wr;
 			context.RegisterObject(this, "Internal", false);
@@ -55,17 +55,27 @@ namespace OpenRA.Mods.RA.Scripting
 			context.RegisterType(typeof(WRange), "WRange", true);
 			context.RegisterType(typeof(int2), "int2", true);
 			context.RegisterType(typeof(float2), "float2", true);
+
 			var sharedScripts = Game.modData.Manifest.LuaScripts ?? new string[0];
 			if (sharedScripts.Any())
 				context.LoadLuaScripts(f => FileSystem.Open(f).ReadAllText(), sharedScripts);
+
+			AddMapActorGlobals();
+
 			context.LoadLuaScripts(f => w.Map.Container.GetContent(f).ReadAllText(), info.LuaScripts);
+
 			context.InvokeLuaFunction("WorldLoaded");
 		}
 
 		void AddMapActorGlobals()
 		{
 			foreach (var kv in world.WorldActor.Trait<SpawnMapActors>().Actors)
-				context.Lua[kv.Key] = kv.Value;
+			{
+				if (context.Lua[kv.Key] != null)
+					context.ShowErrorMessage("{0}: The global name '{1}' is reserved and may not be used by map actor {2}".F(GetType().Name, kv.Key, kv.Value), null);
+				else
+					context.Lua[kv.Key] = kv.Value;
+			}
 		}
 
 		public void Tick(Actor self)