diff --git a/.travis.yml b/.travis.yml
index a7af76a..cfa4dad 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,9 +1,8 @@
 language: php
 
 php:
-  - 5.4
-  - 5.5
   - 5.6
+  - 7.0
 
 before_script:
   - composer install
diff --git a/lib/Migrator.php b/lib/Migrator.php
index 8b3a6be..eac6d09 100644
--- a/lib/Migrator.php
+++ b/lib/Migrator.php
@@ -41,7 +41,7 @@ public function __construct(
     public function initialize()
     {
         if ($this->versionStorage->hasVersioningNode()) {
-            throw MigratorException('Will not re-initialize');
+            throw new MigratorException('This repository has already been initialized. Will not re-initialize.');
         }
 
         foreach (array_keys($this->versionCollection->getAllVersions()) as $timestamp) {
diff --git a/tests/Functional/MigrationTest.php b/tests/Functional/MigrationTest.php
index 64f270a..4963b18 100644
--- a/tests/Functional/MigrationTest.php
+++ b/tests/Functional/MigrationTest.php
@@ -159,6 +159,20 @@ public function testInitialize()
         $this->assertCount(2, $nodes);
     }
 
+    /**
+     * It should throw an exception if trying to reiniitialize.
+     *
+     * @expectedException PHPCR\Migrations\Exception\MigratorException
+     * @expectedExceptionMessage Will not re-initialize
+     */
+    public function testReinitialize()
+    {
+        $this->addVersion(self::VERSION1);
+        $this->addVersion(self::VERSION2);
+        $this->getMigrator()->initialize();
+        $this->getMigrator()->initialize();
+    }
+
     /**
      * It should migrate to the next version.
      */