diff --git a/gns3server/modules/iou/iou_vm.py b/gns3server/modules/iou/iou_vm.py
index 8a3d55d8..9237dcaf 100644
--- a/gns3server/modules/iou/iou_vm.py
+++ b/gns3server/modules/iou/iou_vm.py
@@ -385,7 +385,7 @@ class IOUVM(BaseVM):
         except configparser.Error as e:
             raise IOUError("Could not parse iourc file {}: {}".format(self.iourc_path, e))
         except UnicodeDecodeError as e:
-            raise IOUError("Invalid iourc file {}: {}".format(self.iourc_path, e))
+            raise IOUError("Non ascii characters in iourc file {}, please remove them: {}".format(self.iourc_path, e))
         if "license" not in config:
             raise IOUError("License section not found in iourc file {}".format(self.iourc_path))
         hostname = socket.gethostname()