diff --git a/inspect.lua b/inspect.lua
index 1e982ca..c8bb684 100644
--- a/inspect.lua
+++ b/inspect.lua
@@ -21,8 +21,8 @@ end
 local function prepareObject(other)
     assert(type(other) == "table", "object has to be a table")
     local keys = {}
-    for key, _ in pairs(other) do
-        keys.insert(key)
+    for k, _ in pairs(other) do
+        table.insert(keys, k)
     end
     table.sort(keys)
     return other, keys