diff --git a/src/Index/Index.php b/src/Index/Index.php
index 7a13529..9cb975e 100644
--- a/src/Index/Index.php
+++ b/src/Index/Index.php
@@ -26,7 +26,7 @@ class Index implements ReadableIndex, \Serializable
      *
      * @var string[][]
      */
-    public $references = [];
+    private $references = [];
 
     /**
      * @var bool
@@ -150,6 +150,17 @@ class Index implements ReadableIndex, \Serializable
         return $this->references[$fqn] ?? [];
     }
 
+    /**
+     * For test use.
+     * Returns all references, keyed by fqn.
+     *
+     * @return string[][]
+     */
+    public function getReferences(): array
+    {
+        return $this->references;
+    }
+
     /**
      * Adds a document URI as a referencee of a specific symbol
      *
diff --git a/tests/Validation/ValidationTest.php b/tests/Validation/ValidationTest.php
index 7957fc1..1145df0 100644
--- a/tests/Validation/ValidationTest.php
+++ b/tests/Validation/ValidationTest.php
@@ -103,7 +103,7 @@ class ValidationTest extends TestCase
 
         $document = new PhpDocument($filename, $fileContents, $index, $parser, $docBlockFactory, $definitionResolver);
 
-        $actualRefs = $index->references;
+        $actualRefs = $index->getReferences();
         $this->filterSkippedReferences($actualRefs);
         $actualDefs = $this->getTestValuesFromDefs($document->getDefinitions());