diff --git a/README.md b/README.md
index 2ed3e4e5..5b6dda3a 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ Relative to `boost::ratio`:
 ### install dependencies
 
 - [github/Rconybea/xo-cmake](https://github.com/Rconybea/xo-cmake) cmake macros
+- [github/rconybea/xo-indentlog](https://github.com/Rconybea/xo-indentlog) logging (used by unit tests)
 - [github/Rconybea/xo-flatstring](https://github.com/Rconybea/xo-flatstring) fixed-capacity strings
 
 ### clone xo-ratio