diff --git a/nixos/doc/manual/installation/installing-usb.xml b/nixos/doc/manual/installation/installing-usb.xml
index a4b5dafbed16..dae733060569 100644
--- a/nixos/doc/manual/installation/installing-usb.xml
+++ b/nixos/doc/manual/installation/installing-usb.xml
@@ -11,7 +11,9 @@ a USB stick. You can use the <command>dd</command> utility to write the image:
 <command>dd if=<replaceable>path-to-image</replaceable>
 of=<replaceable>/dev/sdb</replaceable></command>. Be careful about specifying the
 correct drive; you can use the <command>lsblk</command> command to get a list of
-block devices.</para>
+block devices. If you're on OS X you can run <command>diskutil list</command>
+to see the list of devices; the device you'll use for the USB must be ejected
+before writing the image.</para>
 
 <para>The <command>dd</command> utility will write the image verbatim to the drive,
 making it the recommended option for both UEFI and non-UEFI installations. For