diff --git a/docs/install.rst b/docs/install.rst
index 06745d1..e17d5e9 100644
--- a/docs/install.rst
+++ b/docs/install.rst
@@ -17,7 +17,7 @@ Requirements
 - Libgit2 v0.22.x
 - cffi 0.8.1+
 - Libssh2, optional, used for SSH network operations.
-- pkg-config
+- pkg-config, optional, used for SSH network operations.
 
 .. warning::