diff --git a/CHANGELOG.md b/CHANGELOG.md
index bbe08fb9..d82b5b50 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Overcommit Changelog
 
+## 0.66.0
+
+* Add `--diff` CLI option for running pre-commit hooks against only changed files
+
 ## 0.65.0
 
 * Load bundled gems on expected version
diff --git a/README.md b/README.md
index 877e9396..a0d46726 100644
--- a/README.md
+++ b/README.md
@@ -131,6 +131,7 @@ Command Line Flag         | Description
 `-f`/`--force`            | Don't bail on install if other hooks already exist--overwrite them
 `-l`/`--list-hooks`       | Display all available hooks in the current repository
 `-r`/`--run`              | Run pre-commit hook against all tracked files in repository
+`--diff <ref>`            | Run pre-commit hook against all changed files relative to `<ref>`
 `-t`/`--template-dir`     | Print location of template directory
 `-h`/`--help`             | Show command-line flag documentation
 `-v`/`--version`          | Show version
diff --git a/lib/overcommit/version.rb b/lib/overcommit/version.rb
index 0b718a39..c1091e52 100644
--- a/lib/overcommit/version.rb
+++ b/lib/overcommit/version.rb
@@ -2,5 +2,5 @@
 
 # Defines the gem version.
 module Overcommit
-  VERSION = '0.65.0'
+  VERSION = '0.66.0'
 end