diff --git a/docs/usage.md b/docs/usage.md
index 68e4dd0..69bd2dc 100644
--- a/docs/usage.md
+++ b/docs/usage.md
@@ -102,6 +102,11 @@ $ dotdrop compare
 The diffing is done with the UNIX tool `diff` as the backend; one can provide a specific
 diff command using the config entry `diff_command`.
 
+You can specify against which destination file to compare:
+```bash
+$ dotdrop compare -C ~/.vimrc
+```
+
 To ignore specific patterns, see [the ignore patterns](config.md#ignore-patterns).
 
 To completely ignore all files not present in `dotpath` see [Ignore missing](#ignore-missing).