diff --git a/lib/XCollectionService.lua b/lib/XCollectionService.lua
index 43fc458..77e7702 100644
--- a/lib/XCollectionService.lua
+++ b/lib/XCollectionService.lua
@@ -6,7 +6,7 @@ Class.__index = function(inst, key)
     -- Since this is an extension wrapper for CollectionService, just return CollectionService's version
 
     if not CollectionService[key] then
-        error("Attempt to index " + tostring(key) + ", a nil value", 2)
+        error("Attempt to index " .. tostring(key) .. ", a nil value", 2)
     end
     
 	if type(CollectionService[key]) == "function" then
@@ -380,4 +380,4 @@ return {
         end
         return instance
     end
-}
\ No newline at end of file
+}