1 files changed, 2 insertions, 1 deletions

diff --git a/BUGS b/BUGS
index ed336a4d2..4bcb0a82a 100644
--- a/BUGS
+++ b/BUGS
@@ -42,7 +42,8 @@ Known bugs:
   correctly in a reduced exponent range.
 
 * The mpfr_acos function fails or is very inefficient (very slow and
-  takes a lot of memory) on tiny arguments.
+  takes a lot of memory) on tiny arguments. The way the intermediate
+  precision is neither documented nor proved and looks strange.
 
 Potential bugs: