Updated point in Notes section

README.md

@@ -31,7 +31,9 @@ json.decode('[1,2,3,{"x":10}]') -- Returns { 1, 2, 3, { x = 10 } }
 ```
 
 ## Notes
-* Tables with the key `1` set are treated as arrays when encoding
+* Trying to encode values which are unrepresentable in JSON will never result
+  in type conversion or other magic: sparse arrays, tables with mixed keys or
+  invalid numbers (NaN, -inf, inf) will raise an error
 * `null` values contained within an array or object are converted to `nil` and
   are therefore lost upon decoding
 * *Pretty* encoding is not supported, `json.encode()` only encodes to a compact