add env so homebrew instructions work in fish as well as bash on OS X
diff --git a/docs/hazmat/backends/openssl.rst b/docs/hazmat/backends/openssl.rst
index 355a1eb..a2417cf 100644
--- a/docs/hazmat/backends/openssl.rst
+++ b/docs/hazmat/backends/openssl.rst
@@ -48,7 +48,8 @@
 
 An example using a `Homebrew`_ OpenSSL installation::
 
-    ARCHFLAGS="-arch x86_64" LDFLAGS="-L/usr/local/opt/openssl/lib" CFLAGS="-I/usr/local/opt/openssl/include" pip install cryptography
+    env ARCHFLAGS="-arch x86_64" LDFLAGS="-L/usr/local/opt/openssl/lib" CFLAGS="-I/usr/local/opt/openssl/include" pip install cryptography
+
 
 .. _`OpenSSL`: https://www.openssl.org/
 .. _`Homebrew`: http://brew.sh