diff --git a/src/serpent.lua b/src/serpent.lua
index 6961a24..dabfe95 100644
--- a/src/serpent.lua
+++ b/src/serpent.lua
@@ -1,4 +1,4 @@
-local n, v = "serpent", 0.283 -- (C) 2012-15 Paul Kulchenko; MIT License
+local n, v = "serpent", 0.284 -- (C) 2012-15 Paul Kulchenko; MIT License
 local c, d = "Paul Kulchenko", "Lua serializer and pretty printer"
 local snum = {[tostring(1/0)]='1/0 --[[math.huge]]',[tostring(-1/0)]='-1/0 --[[-math.huge]]',[tostring(0/0)]='0/0'}
 local badtype = {thread = true, userdata = true, cdata = true}
@@ -9,7 +9,7 @@ for _,k in ipairs({'and', 'break', 'do', 'else', 'elseif', 'end', 'false',
   'return', 'then', 'true', 'until', 'while'}) do keyword[k] = true end
 for k,v in pairs(G) do globals[v] = k end -- build func to name mapping
 for _,g in ipairs({'coroutine', 'debug', 'io', 'math', 'string', 'table', 'os'}) do
-  for k,v in pairs(G[g] or {}) do globals[v] = g..'.'..k end end
+  for k,v in pairs(type(G[g]) == 'table' and G[g] or {}) do globals[v] = g..'.'..k end end
 
 local function s(t, opts)
   local name, indent, fatal, maxnum = opts.name, opts.indent, opts.fatal, opts.maxnum