Mobilespec crashes on iPhone 6 simulator

Jun 29 19:08:54 dbexecutor.local mobilespec[5854]: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSConcreteData base64EncodedString]: unrecognized selector sent to instance 0x796be580'
	*** First throw call stack:
	(
		0   CoreFoundation                      0x01a7d746 __exceptionPreprocess + 182
		1   libobjc.A.dylib                     0x016d8a97 objc_exception_throw + 44
		2   CoreFoundation                      0x01a85705 -[NSObject(NSObject) doesNotRecognizeSelector:] + 277
		3   CoreFoundation                      0x019cc287 ___forwarding___ + 1047
		4   CoreFoundation                      0x019cbe4e _CF_forwarding_prep_0 + 14
		5   mobilespec                          0x0010565f __25-[CDVFile readAsDataURL:]_block_invoke_2 + 255
		6   mobilespec                          0x0010d7db -[CDVLocalFilesystem readFileAtURL:start:end:callback:] + 539
		7   mobilespec                          0x0010551a __25-[CDVFile readAsDataURL:]_block_invoke + 202
		8   libdispatch.dylib                   0x03672d8a _dispatch_call_block_and_release + 15
		9   libdispatch.dylib                   0x0368fecf _dispatch_client_callout + 14
		10  libdispatch.dylib                   0x0367a348 _dispatch_root_queue_drain + 745
		11  libdispatch.dylib                   0x0367b3e7 _dispatch_worker_thread3 + 108
		12  libsystem_pthread.dylib             0x039cf1da _pthread_wqthread + 724
		13  libsystem_pthread.dylib             0x039cce2e start_wqthread + 30
	)
Jun 29 19:08:55 dbexecutor com.apple.CoreSimulator.SimDevice.D1704D22-3CBA-45D4-A2C6-B30A8CC30799.launchd_sim[5712] (UIKitApplication:org.apache.mobilespec[0x11c6][5854]): Service exited due to signal: Abort trap: 6