diff --git a/README.md b/README.md
index e457567..71e7fa0 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,10 @@
 
 a simple shift register built on piperw(1)
 
+requirements:
+- execline (obviously)
+- s6-portable-utils (s6-expr, s6-ls, s6-tail)
+
 ### usage
 
 ```