diff --git a/README.md b/README.md
index cf1b392..0552abf 100644
--- a/README.md
+++ b/README.md
@@ -125,7 +125,7 @@ _Total timing_ is computed from individual solution _timings_ and excludes as mu
 cargo test
 ```
 
-To run tests for a specific day, append `--bin <day>`, e.g. `cargo test --bin 01`. You can further scope it down to a specific part, e.g. `cargo test --bin 01 part_one`.
+To run tests for a specific day, append `--lib <day>`, e.g. `cargo test --lib 01`. You can further scope it down to a specific part, e.g. `cargo test --lib 01 part_one`.
 
 ### Format code