diff --git a/inspect.lua b/inspect.lua
index 7cbb3fa..7a9786e 100644
--- a/inspect.lua
+++ b/inspect.lua
@@ -54,19 +54,24 @@ local function isIdentifier(str)
 end
 
 local function isArrayKey(k, length)
-  return type(k)=='number' and 1 <= k and k <= length
+  return type(k) == 'number' and 1 <= k and k <= length
 end
 
 local function isDictionaryKey(k, length)
   return not isArrayKey(k, length)
 end
 
-local sortOrdersByType = {
+local sortOrdersByType = setmetatable({
   ['number']   = 1, ['boolean']  = 2, ['string'] = 3, ['table'] = 4,
   ['function'] = 5, ['userdata'] = 6, ['thread'] = 7
-}
+},
+{ __index = function (t, k)
+  if not rawget(t, k) then
+    return math.huge
+  end
+end })
 
-local function sortKeys(a,b)
+local function sortKeys(a, b)
   local ta, tb = type(a), type(b)
   if ta ~= tb then return sortOrdersByType[ta] < sortOrdersByType[tb] end
   if ta == 'string' or ta == 'number' then return a < b end
@@ -77,7 +82,7 @@ local function getDictionaryKeys(t)
   local length = #t
   local keys = {}
   for k,_ in pairs(t) do
-    if isDictionaryKey(k, length) then table.insert(keys,k) end
+    if isDictionaryKey(k, length) then table.insert(keys, k) end
   end
   table.sort(keys, sortKeys)
   return keys
@@ -93,6 +98,26 @@ local function getToStringResultSafely(t, mt)
   return string
 end
 
+local inspectorMaxIdsMetaTable = {
+  __index = function (t, k)
+    if not rawget(t, k) then
+      rawset(t, k, 0)
+    end
+    return 0
+  end
+}
+
+local inspectorIdsMetaTable = {
+  __index = function (t, k)
+    local v = rawget(t, k)
+    if not v then
+      rawset(t, k, setmetatable({}, {__mode = "kv"}))
+      v = rawget(t, k)
+    end
+    return v
+  end
+}
+
 local Inspector = {}
 
 function Inspector:new(t, depth)
@@ -100,18 +125,8 @@ function Inspector:new(t, depth)
     buffer = {},
     depth = depth,
     level = 0,
-    maxIds = {
-      ['function'] = 0,
-      ['userdata'] = 0,
-      ['thread']   = 0,
-      ['table']    = 0
-    },
-    ids = {
-      ['function'] = setmetatable({}, {__mode = "kv"}),
-      ['userdata'] = setmetatable({}, {__mode = "kv"}),
-      ['thread']   = setmetatable({}, {__mode = "kv"}),
-      ['table']    = setmetatable({}, {__mode = "kv"})
-    },
+    maxIds = setmetatable({}, inspectorMaxIdsMetaTable),
+    ids = setmetatable({}, inspectorIdsMetaTable),
     tableAppearances = setmetatable({}, {__mode = "k"})
   }
 
diff --git a/spec/inspect_spec.lua b/spec/inspect_spec.lua
index 71a15f3..c0ae8c8 100644
--- a/spec/inspect_spec.lua
+++ b/spec/inspect_spec.lua
@@ -1,4 +1,5 @@
 local inspect = require 'inspect'
+local is_luajit, ffi = pcall(require, 'ffi')
 
 describe( 'inspect', function()
 
@@ -42,6 +43,14 @@ describe( 'inspect', function()
     assert.equals(inspect(false), 'false')
   end)
 
+  if is_luajit then
+    describe('luajit cdata', function()
+      it('works with luajit cdata', function()
+        assert.equals(inspect({ ffi.new("int", 1), ffi.typeof("int"), ffi.typeof("int")(1) }), '{ <cdata 1>, <cdata 2>, <cdata 3> }')
+      end)
+    end)
+  end
+
   describe('tables', function()
 
     it('works with simple array-like tables', function()
@@ -61,7 +70,7 @@ describe( 'inspect', function()
         [print] = 1, ["buy more"] = 1, a = 1,
         [14] = 1, [{c=2}] = 1, [true]= 1
       }
-      assert.equals(inspect(t), [[{ 1, 2, 3,
+      local s = [[{ 1, 2, 3,
   [14] = 1,
   [true] = 1,
   a = 1,
@@ -69,8 +78,12 @@ describe( 'inspect', function()
   [{
     c = 2
   }] = 1,
-  [<function 1>] = 1
-}]])
+  [<function 1>] = 1]]
+      if is_luajit then
+	    t[ffi.new("int", 1)] = 1
+		s = s .. ",\n  [<cdata 1>] = 1"
+      end
+      assert.equals(inspect(t), s .. "\n}")
     end)
 
     it('works with nested dictionary tables', function()