diff --git a/tilecache/TileCache/Service.py b/tilecache/TileCache/Service.py
index 9d6aa16..7352882 100755
--- a/tilecache/TileCache/Service.py
+++ b/tilecache/TileCache/Service.py
@@ -34,7 +34,9 @@ def getLayer(self, layername):
         try:
             return self.service.layers[layername]
         except:
-            raise TileCacheException("The requested layer (%s) does not exist. Available layers are: \n * %s" % (layername, "\n * ".join(self.service.layers.keys()))) 
+            layer_names = self.service.layers.keys()
+            layer_names.sort()
+            raise TileCacheException("The requested layer (%s) does not exist. Available layers are: \n * %s" % (layername, "\n * ".join(layer_names))) 
 
 def import_module(name):
     """Helper module to import any module based on a name, and return the module."""