diff --git a/.travis.yml b/.travis.yml
index df030c2..93c6d5e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,13 +2,11 @@ sudo: false
 
 dist: trusty
 
-cache:
-  apt: true
-
 language: php
 
 ## Cache composer downloads.
 cache:
+  apt: true
   directories:
     - $HOME/.cache/composer/files
 
@@ -41,7 +39,10 @@ script:
     fi
 
   # Test the ruleset.
-  - vendor/bin/phpcs ./Test/PasswordCompatTest.php --standard=PHPCompatibilityPasswordCompat --runtime-set testVersion 5.4
+  - vendor/bin/phpcs ./Test/PasswordCompatTest.php --standard=PHPCompatibilityPasswordCompat --runtime-set testVersion 5.4-
+
+  # Check that the ruleset does not throw unnecessary errors for the compat library itself.
+  - vendor/bin/phpcs ./vendor/ircmaxell/ --standard=PHPCompatibilityPasswordCompat --runtime-set testVersion 5.4- --ignore=/password-compat/test/*
 
   # Validate the composer.json file.
   # @link https://getcomposer.org/doc/03-cli.md#validate
diff --git a/composer.json b/composer.json
index 1755b7c..7af4b05 100644
--- a/composer.json
+++ b/composer.json
@@ -21,7 +21,8 @@
     "phpcompatibility/php-compatibility" : "^9.0"
   },
   "require-dev" : {
-    "dealerdirect/phpcodesniffer-composer-installer": "^0.5"
+    "dealerdirect/phpcodesniffer-composer-installer": "^0.5",
+    "ircmaxell/password-compat": "dev-master"
   },
   "suggest" : {
     "dealerdirect/phpcodesniffer-composer-installer": "^0.5 || This Composer plugin will sort out the PHP_CodeSniffer 'installed_paths' automatically.",