diff --git a/moonscript/util.lua b/moonscript/util.lua
index 714767e..83d7e37 100644
--- a/moonscript/util.lua
+++ b/moonscript/util.lua
@@ -103,7 +103,7 @@ dump = function(what)
       end
       seen[what] = false
       local class_name
-      if what.__class then
+      if type(what.__class) == "table" and type(what.__class.__name) == "string" then
         class_name = "<" .. tostring(what.__class.__name) .. ">"
       end
       return tostring(class_name or "") .. "{\n" .. concat(lines) .. (" "):rep((depth - 1) * 4) .. "}\n"
diff --git a/moonscript/util.moon b/moonscript/util.moon
index 9516c8b..9969ac4 100644
--- a/moonscript/util.moon
+++ b/moonscript/util.moon
@@ -70,7 +70,7 @@ dump = (what) ->
 
       seen[what] = false
 
-      class_name = if what.__class
+      class_name = if type(what.__class) == "table" and type(what.__class.__name) == "string"
         "<#{what.__class.__name}>"
 
       "#{class_name or ""}{\n" .. concat(lines) .. (" ")\rep((depth - 1)*4) .. "}\n"