diff --git a/README.md b/README.md
index 999c4f47..7a275d9a 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,7 @@ To add options that require quotes ("), escape them with \". For example, so use
 nvs_set autoexec2 str -v "squeezelite -o \"BT -n 'MySpeaker'\" -b 500:2000 -R -u m -Z 192000 -r \"44100-44100\""
 
 # Additional misc notes to do you build
+- as of this writing, ESP-IDF has a bug int he way the PLL values are calculated for i2s, so you *must* use the i2s.c file in the patch directory
 - for all libraries, add -mlongcalls. 
 - audio libraries are complicated to rebuild, open an issue if you really want to
 - libmad, libflac (no esp's version), libvorbis (tremor - not esp's version), alac work