diff --git a/docs/CommandGuide/opt.pod b/docs/CommandGuide/opt.pod
index daf1040..d1d1db5 100644
--- a/docs/CommandGuide/opt.pod
+++ b/docs/CommandGuide/opt.pod
@@ -38,6 +38,12 @@
 
 =over
 
+=item B<-f>
+
+Enable binary output on terminals.  Normally, B<opt> will refuse to
+write raw bitcode output if the output stream is a terminal. With this option,
+B<opt> will write raw bitcode regardless of the output device.
+
 =item B<-help>
 
 Print a summary of command line options.