diff --git a/timeseriesviewer/timeseries.py b/timeseriesviewer/timeseries.py
index a007012f6f28ef13afb52936533d038b1d35c2af..4ecce59df5b766e9680c61947c79a00d95c5c879 100644
--- a/timeseriesviewer/timeseries.py
+++ b/timeseriesviewer/timeseries.py
@@ -383,12 +383,9 @@ class TimeSeries(QObject):
         lines = []
         lines.append('#Time series definition file: {}'.format(np.datetime64('now').astype(str)))
         lines.append('#<image path>[;<mask path>]')
-        for TSD in self.data.values():
+        for TSD in self.data:
 
             line = TSD.pathImg
-            if TSD.pathMsk is not None:
-                line += TimeSeries._sep + TSD.pathMsk
-
             lines.append(line)
 
         lines = [l+'\n' for l in lines]
@@ -444,6 +441,7 @@ class TimeSeries(QObject):
         self.removeDates(self[:])
 
 
+
     def removeDates(self, TSDs):
         removed = list()
         for TSD in TSDs: