diff --git a/spec/Config/Version2SerializerSpec.php b/spec/Config/Version2SerializerSpec.php
index f76e987..89b1c04 100644
--- a/spec/Config/Version2SerializerSpec.php
+++ b/spec/Config/Version2SerializerSpec.php
@@ -16,4 +16,9 @@ function it_stores_paths_alphabetically()
     {
         $this->serializePaths(['foo', 'bar'])->shouldReturn(['paths' => ['bar', 'foo']]);
     }
+
+    function it_deduplicates_paths()
+    {
+        $this->serializePaths(['foo', 'bar', 'foo'])->shouldReturn(['paths' => ['bar', 'foo']]);
+    }
 }
diff --git a/src/Config/Version2Serializer.php b/src/Config/Version2Serializer.php
index 9107bf3..7aed35e 100644
--- a/src/Config/Version2Serializer.php
+++ b/src/Config/Version2Serializer.php
@@ -12,6 +12,6 @@ public function deserializePaths($obj)
     public function serializePaths(array $paths)
     {
         sort($paths);
-        return ['paths' => array_values($paths)];
+        return ['paths' => array_unique(array_values($paths))];
     }
 }