diff --git a/README.md b/README.md
index 431532c..b90b7b0 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,11 @@ In practice, most implementations fall short of these goals, due to a variety of
 
 Here we test a small sample of regular expressions that are known to be hard to match properly against a couple of popular regex engines.
 
+## Warning
+
+It is not clear whether the author's interpretation of the standard is actually correct in all cases.
+One can still observe that implementations show different behaviour in these situations.
+
 ## Run it
 
 Build using Lix: