diff --git a/OpenRA.Game/FileSystem/FileSystem.cs b/OpenRA.Game/FileSystem/FileSystem.cs
index f34f1534fa..11b3baae10 100644
--- a/OpenRA.Game/FileSystem/FileSystem.cs
+++ b/OpenRA.Game/FileSystem/FileSystem.cs
@@ -297,5 +297,40 @@ namespace OpenRA.FileSystem
 
 			return fileIndex.ContainsKey(filename);
 		}
+
+		/// <summary>
+		/// Resolves a filesystem for an assembly, accounting for explicit and mod mounts.
+		/// Assemblies must exist in the native OS file system (not inside an OpenRA-defined package).
+		/// </summary>
+		public static string ResolveAssemblyPath(string path, Manifest manifest, InstalledMods installedMods)
+		{
+			var explicitSplit = path.IndexOf('|');
+			if (explicitSplit > 0)
+			{
+				var parent = path.Substring(0, explicitSplit);
+				var filename = path.Substring(explicitSplit + 1);
+
+				var parentPath = manifest.Packages.FirstOrDefault(kv => kv.Value == parent).Key;
+				if (parentPath == null)
+					return null;
+
+				if (parentPath.StartsWith("$", StringComparison.Ordinal))
+				{
+					Manifest mod;
+					if (!installedMods.TryGetValue(parentPath.Substring(1), out mod))
+						return null;
+
+					if (!(mod.Package is Folder))
+						return null;
+
+					 path = Path.Combine(mod.Package.Name, filename);
+				}
+				else
+					path = Path.Combine(parentPath, filename);
+			}
+
+			var resolvedPath = Platform.ResolvePath(path);
+			return File.Exists(resolvedPath) ? resolvedPath : null;
+		}
 	}
 }
diff --git a/OpenRA.Game/ModData.cs b/OpenRA.Game/ModData.cs
index 4b5e3c6a6d..d73ccda644 100644
--- a/OpenRA.Game/ModData.cs
+++ b/OpenRA.Game/ModData.cs
@@ -49,13 +49,13 @@ namespace OpenRA
 		{
 			Languages = new string[0];
 
-			ModFiles = new FS(mods);
 
 			// Take a local copy of the manifest
 			Manifest = new Manifest(mod.Id, mod.Package);
-			ModFiles.LoadFromManifest(Manifest);
+			ObjectCreator = new ObjectCreator(Manifest, mods);
 
-			ObjectCreator = new ObjectCreator(Manifest, ModFiles);
+			ModFiles = new FS(mods);
+			ModFiles.LoadFromManifest(Manifest);
 			Manifest.LoadCustomData(ObjectCreator);
 
 			if (useLoadScreen)
diff --git a/OpenRA.Game/ObjectCreator.cs b/OpenRA.Game/ObjectCreator.cs
index e4cc1072af..cd45fda8ff 100644
--- a/OpenRA.Game/ObjectCreator.cs
+++ b/OpenRA.Game/ObjectCreator.cs
@@ -27,40 +27,31 @@ namespace OpenRA
 		readonly Cache<string, Type> typeCache;
 		readonly Cache<Type, ConstructorInfo> ctorCache;
 		readonly Pair<Assembly, string>[] assemblies;
-		readonly bool isMonoRuntime = Type.GetType("Mono.Runtime") != null;
 
-		public ObjectCreator(Manifest manifest, FileSystem.FileSystem modFiles)
+		public ObjectCreator(Manifest manifest, InstalledMods mods)
 		{
 			typeCache = new Cache<string, Type>(FindType);
 			ctorCache = new Cache<Type, ConstructorInfo>(GetCtor);
 
 			// Allow mods to load types from the core Game assembly, and any additional assemblies they specify.
+			// Assemblies can only be loaded from directories to avoid circular dependencies on package loaders.
 			var assemblyList = new List<Assembly>() { typeof(Game).Assembly };
 			foreach (var path in manifest.Assemblies)
 			{
-				var data = modFiles.Open(path).ReadAllBytes();
+				var resolvedPath = FileSystem.FileSystem.ResolveAssemblyPath(path, manifest, mods);
+				if (resolvedPath == null)
+					throw new FileNotFoundException("Assembly `{0}` not found.".F(path));
 
 				// .NET doesn't provide any way of querying the metadata of an assembly without either:
 				//   (a) loading duplicate data into the application domain, breaking the world.
 				//   (b) crashing if the assembly has already been loaded.
 				// We can't check the internal name of the assembly, so we'll work off the data instead
-				var hash = CryptoUtil.SHA1Hash(data);
+				var hash = CryptoUtil.SHA1Hash(File.ReadAllBytes(resolvedPath));
 
 				Assembly assembly;
 				if (!ResolvedAssemblies.TryGetValue(hash, out assembly))
 				{
-					Stream symbolStream = null;
-					var hasSymbols = false;
-
-					// Mono has its own symbol format.
-					if (isMonoRuntime)
-						hasSymbols = modFiles.TryOpen(path + ".mdb", out symbolStream);
-
-					// .NET uses .pdb files.
-					else
-						hasSymbols = modFiles.TryOpen(path.Substring(0, path.Length - 4) + ".pdb", out symbolStream);
-
-					assembly = hasSymbols ? Assembly.Load(data, symbolStream.ReadAllBytes()) : Assembly.Load(data);
+					assembly = Assembly.LoadFile(resolvedPath);
 					ResolvedAssemblies.Add(hash, assembly);
 				}