diff --git a/README.md b/README.md
index 9751c00..69568eb 100644
--- a/README.md
+++ b/README.md
@@ -179,7 +179,9 @@ the following commandline options:
   - `--top-keys comma,separated,keys` - Keys to keep at the top of mappings.
 
 #### `requirements-txt-fixer`
-Sorts entries in requirements.txt and constraints.txt and removes incorrect entry for `pkg-resources==0.0.0`
+Sorts entries in requirements.txt and constraints.txt and removes incorrect entry for `pkg-resources==0.0.0`. Optionally flags packages that are missing
+a version string. You can configure this with the following commandline options:
+  - `--require_version` - Fail if any package is missing a version string.
 
 #### `sort-simple-yaml`
 Sorts simple YAML files which consist only of top-level