diff --git a/docs/hazmat/backends/openssl.rst b/docs/hazmat/backends/openssl.rst
index d6351c9..547fe76 100644
--- a/docs/hazmat/backends/openssl.rst
+++ b/docs/hazmat/backends/openssl.rst
@@ -3,7 +3,9 @@
 OpenSSL Backend
 ===============
 
-The `OpenSSL`_ C library.
+The `OpenSSL`_ C library. Cryptography supports version ``0.9.8e`` (present in
+Red Hat Enterprise Linux 5) and greater. Earlier versions may work but are
+**not tested or supported**.
 
 .. data:: cryptography.hazmat.backends.openssl.backend
 
diff --git a/docs/hazmat/bindings/commoncrypto.rst b/docs/hazmat/bindings/commoncrypto.rst
index 50dbe69..e5a673b 100644
--- a/docs/hazmat/bindings/commoncrypto.rst
+++ b/docs/hazmat/bindings/commoncrypto.rst
@@ -7,8 +7,8 @@
 
 .. versionadded:: 0.2
 
-These are `CFFI`_ bindings to the `CommonCrypto`_ C library. It is available on
-Mac OS X.
+These are `CFFI`_ bindings to the `CommonCrypto`_ C library. It is only
+available on Mac OS X versions 10.8 and above.
 
 .. class:: cryptography.hazmat.bindings.commoncrypto.binding.Binding()
 
diff --git a/docs/hazmat/bindings/openssl.rst b/docs/hazmat/bindings/openssl.rst
index 557f8c4..9fce8f7 100644
--- a/docs/hazmat/bindings/openssl.rst
+++ b/docs/hazmat/bindings/openssl.rst
@@ -5,7 +5,9 @@
 
 .. currentmodule:: cryptography.hazmat.bindings.openssl.binding
 
-These are `CFFI`_ bindings to the `OpenSSL`_ C library.
+These are `CFFI`_ bindings to the `OpenSSL`_ C library. Cryptography supports
+version ``0.9.8e`` (present in Red Hat Enterprise Linux 5) and greater. Earlier
+versions may work but are **not tested or supported**.
 
 .. class:: cryptography.hazmat.bindings.openssl.binding.Binding()