diff --git a/lume.lua b/lume.lua
index 9a179f4..51834ba 100644
--- a/lume.lua
+++ b/lume.lua
@@ -30,7 +30,9 @@ local absindex = function(len, i)
 end
 
 local iscallable = function(x)
-  return type(x) == "function" or getmetatable(x).__call ~= nil
+  if type(x) == "function" then return true end
+  local mt = getmetatable(x)
+  return mt and mt.__call ~= nil
 end