diff --git a/tests/Whoops/Exception/FrameTest.php b/tests/Whoops/Exception/FrameTest.php
index 72c6250..5356c6f 100644
--- a/tests/Whoops/Exception/FrameTest.php
+++ b/tests/Whoops/Exception/FrameTest.php
@@ -103,6 +103,20 @@ class FrameTest extends TestCase
         $this->assertStringEqualsFile($data['file'], $frame->getFileContents());
     }
 
+    /**
+     * @covers Whoops\Exception\Frame::getFileContents
+     * @testWith ["[internal]"]
+     *           ["Unknown"]
+     * @see https://github.com/filp/whoops/pull/599
+     */
+    public function testGetFileContentsWhenFrameIsNotRelatedToSpecificFile($fakeFilename)
+    {
+        $data  = array_merge($this->getFrameData(), ['file' => $fakeFilename]);
+        $frame = $this->getFrameInstance($data);
+
+        $this->assertNull($frame->getFileContents());
+    }
+
     /**
      * @covers Whoops\Exception\Frame::getFileLines
      */