Updating Anvil ssh keys on mac instructions

content/guides/anvil/creating_ssh_key_pairs_on_mac.md

@@ -9,7 +9,7 @@ used, which is located in the _Utilities_ folder under _Applications_.
 {{< figure src="/images/13598866.png" width="598" height="67" >}}
 
 Start _Terminal_ and run the
-command `ssh-keygen -f ~/Desktop/anvil_key`.  This will create two key
+command `ssh-keygen -m PEM -f ~/Desktop/anvil_key`.  This will create two key
 files on your Desktop, one public and one private, which can later be
 moved to whatever location you prefer.