diff --git a/grammars/README.md b/grammars/README.md
index 7899978ce..886023f77 100644
--- a/grammars/README.md
+++ b/grammars/README.md
@@ -182,7 +182,8 @@ space ::= | " " | "\n" [ \t]{0,20}
 
 Here is also a list of known limitations (contributions welcome):
 
-- `additionalProperties` defaults to `false` (faster grammars + reduces hallucinations)
+- `additionalProperties` defaults to `false` (produces faster grammars + reduces hallucinations).
+- `"additionalProperties": true` may produce keys that contain unescaped newlines.
 - Unsupported features are skipped silently. It is currently advised to use the command-line Python converter (see above) to see any warnings, and to inspect the resulting grammar / test it w/ [llama-gbnf-validator](../examples/gbnf-validator/gbnf-validator.cpp).
 - Can't mix `properties` w/ `anyOf` / `oneOf` in the same type (https://github.com/ggerganov/llama.cpp/issues/7703)
 - [prefixItems](https://json-schema.org/draft/2020-12/json-schema-core#name-prefixitems) is broken (but [items](https://json-schema.org/draft/2020-12/json-schema-core#name-items) works)