diff --git a/docs/installation.rst b/docs/installation.rst
index 28b311c..f2b4089 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -26,8 +26,8 @@
 ----------------------------------
 
 ``cryptography`` should build very easily on GNU/Linux provided you have a C
-compiler and headers for Python and the OpenSSL and libffi libraries available
-on your system.
+compiler, headers for Python (if you're not using Pypy), and headers for the
+OpenSSL and `libffi` libraries available on your system.
 
 Debian and Ubuntu systems
 .........................