Chutzpah reference error

Chutzpah Error Occured:
Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: U. Line 1, position 1.
   at Newtonsoft.Json.JsonTextReader.ParseValue(Char currentChar)
   at Newtonsoft.Json.JsonTextReader.ReadInternal()
   at Newtonsoft.Json.JsonTextReader.Read()
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.ReadForType(JsonReader reader, Type t, JsonConverter propertyConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonConvert.DeserializeObject(String value, Type type, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value, JsonSerializerSettings settings)
   at Newtonsoft.Json.JsonConvert.DeserializeObject[T](String value)
   at Chutzpah.Wrappers.JsonSerializer.Deserialize[T](String response)
   at Chutzpah.TestResultsBuilder.Build(BrowserTestFileResult browserTestFileResult, TestRunnerMode testRunnerMode)
   at Chutzpah.TestRunner.InvokeTestRunner(String headlessBrowserPath, TestOptions options, TestContext testContext, List`1 testResults, TestRunnerMode testRunnerMode, ITestMethodRunnerCallback callback)
   at Chutzpah.TestRunner.ProcessTestPaths(IEnumerable`1 testPaths, TestOptions options, TestRunnerMode testRunnerMode, ITestMethodRunnerCallback callback, List`1 testResults)
 While Running:C:\work\daedalus-src\Daedalus.Web\Private\Specs\libs\fileuploader-jasmine-tests.js



---

first line is a /// <reference path="../../../f1/f2/file.js" />, when that's removed the error doesn't happen.