diff --git a/src/serpent.lua b/src/serpent.lua
index bb7a78b..94284ed 100644
--- a/src/serpent.lua
+++ b/src/serpent.lua
@@ -103,30 +103,31 @@ local function s(t, opts)
   return not name and body..warn or "do local "..body..sepr..tail.."return "..name..sepr.."end"
 end
 
-if not setfenv then -- Lua 5.2+
-  -- based on http://lua-users.org/lists/lua-l/2010-06/msg00314.html
-  -- this assumes f is a function
-  local function findenv(f)
-    local level = 1
-    repeat
-      local name, value = debug.getupvalue(f, level)
-      if name == '_ENV' then return level, value end
-      level = level + 1
-    until name == nil
-    return nil end
-  getfenv = function (f) return(select(2, findenv(f)) or _G) end
-  setfenv = function (f, t)
-    local level = findenv(f)
-    if level then debug.setupvalue(f, level, t) end
-    return f end
-end
-
 local function deserialize(data, opts)
   local f, res = (loadstring or load)('return '..data)
   if not f then f, res = (loadstring or load)(data) end
   if not f then return f, res end
   if opts and opts.safe == false then return pcall(f) end
 
+  local setfenv, getfenv = setfenv, getfenv
+  if not setfenv then -- Lua 5.2+
+    -- based on http://lua-users.org/lists/lua-l/2010-06/msg00314.html
+    -- this assumes f is a function
+    local function findenv(f)
+      local level = 1
+      repeat
+        local name, value = debug.getupvalue(f, level)
+        if name == '_ENV' then return level, value end
+        level = level + 1
+      until name == nil
+      return nil end
+    getfenv = function (f) return(select(2, findenv(f)) or _G) end
+    setfenv = function (f, t)
+      local level = findenv(f)
+      if level then debug.setupvalue(f, level, t) end
+      return f end
+  end
+
   local env = {}
   env._G = setmetatable(env, { __index = getfenv(f) })
   f = setfenv(f, env)