diff --git a/.travis.yml b/.travis.yml
index 92471f16..e6c99d4c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -8,6 +8,7 @@ php:
 env:
   - DEPENDENCIES=""
   - DEPENDENCIES="--prefer-lowest --prefer-stable"
+  - DEPENDENCIES="--classmap-authoritative"
 
 before_script:
   - sh .travis.install.sh
diff --git a/composer.json b/composer.json
index c82b8e87..c455cccc 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,10 @@
     "autoload": {
         "psr-4": {
             "PackageVersions\\": "src/PackageVersions"
-        }
+        },
+        "files": [
+            "src/PackageVersions/Versions.php"
+        ]
     },
     "autoload-dev": {
         "psr-4": {