diff --git a/README.md b/README.md
index bba7d4e..df39fe2 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@ Very silly terminal-based crossword solver. It can play .puz / .ipuz files from
 
 - Requirements: [Go](https://go.dev)
 - Build: `make`
-- Usage: `./bin/crossword <file>.puz`
+- Usage: `./bin/crossword <file>.{ipuz,puz}`
 
 ![demo](demo.gif)