diff --git a/src/utilities/convert/dseries2Q.m b/src/utilities/convert/dseries2Q.m
index 1bd53b2d95d6c69ba9b05852874a1de4eea9b786..879e1ebeebe7801fdb88658123cb24f5a42a09ca 100644
--- a/src/utilities/convert/dseries2Q.m
+++ b/src/utilities/convert/dseries2Q.m
@@ -76,7 +76,7 @@ switch method
             end
         end
         if ds.dates.freq==12
-            lastmonth = ds.dates.time(idq(end), 2);
+            lastmonth = subperiod(ds.dates(idq(end)));
             if lastmonth<expectedlastmonth(dQ(i))
                 warning('The last available day is not the last observed day of %s.', date2string(dQ(i)))
             end