diff --git a/src/python/dm/daq_web_service/service/experimentSessionController.py b/src/python/dm/daq_web_service/service/experimentSessionController.py
index 27fce7d5b36c3dfd87cd7bed7c6f052a44abf8ad..c0697e2a0c87896b7ced6a21a30781cc2ce1ad6c 100755
--- a/src/python/dm/daq_web_service/service/experimentSessionController.py
+++ b/src/python/dm/daq_web_service/service/experimentSessionController.py
@@ -84,7 +84,7 @@ class ExperimentSessionController(DmSessionController):
             raise InvalidRequest('Missing data directory.')
         dataDirectory = Encoder.decode(dataDirectory)
         if not dataDirectory.startswith('/') and not dataDirectory.count('://'):
-            raise InvalidRequest('Data directory must be an absolute path.')
+            raise InvalidRequest('Data directory must be an absolute path: %s' % dataDirectory)
 
         daqInfo = {}
         encodedDaqInfo = kwargs.get('daqInfo')