diff --git a/tests/README b/tests/README
index 10d057d6a0..22e2123cb7 100644
--- a/tests/README
+++ b/tests/README
@@ -44,6 +44,7 @@ The curl Test Suite
   stunnel (for HTTPS and FTPS tests)
   OpenSSH or SunSSH (for SCP, SFTP and SOCKS4/5 tests)
   nghttpx (for HTTP/2 tests)
+  nroff (for --manual tests)
 
  1.2 Port numbers used by test servers