diff --git a/cmd/md-fmt/README.md b/cmd/md-fmt/README.md
index 11b0bc4..68755cf 100644
--- a/cmd/md-fmt/README.md
+++ b/cmd/md-fmt/README.md
@@ -4,4 +4,6 @@ Takes a csv-like file as input and outputs a formatted markdown table with it.
 
 ## Usage
 
-Run `md-fmt -help` for the list of command line arguments.
+Run `md-fmt -help` for the list of command line arguments. For tab-separated
+files, in order for the separator to be passed correcly from the command line to
+the program, use `-sep=$'\t'` to correctly escape the character.