diff --git a/Program.cs b/Program.cs
index 45317c4..e889f9e 100644
--- a/Program.cs
+++ b/Program.cs
@@ -9,7 +9,7 @@ builder.Services.AddControllers().AddJsonOptions(o => o.JsonSerializerOptions.Pr
 
 builder.Services.AddMemoryCache(o => o.SizeLimit = 128L * 1024 * 1024);
 
-string assetDir = Path.GetFullPath("../tiles1705");
+string assetDir = assetDir = Environment.GetEnvironmentVariable("ASSET_PATH_RO") ?? throw new InvalidOperationException("dir not found");
 
 builder.Services.AddSingleton<TileCache>();
 builder.Services.AddSingleton(provider => new TileLoader(provider.GetRequiredService<TileCache>(), assetDir));