diff --git a/mlair/helpers/filter.py b/mlair/helpers/filter.py
index 543cff3624577ac617733b8b593c5f52f25196b3..36c93b04486fc9be013af2c4f34d2b3ee1bd84c2 100644
--- a/mlair/helpers/filter.py
+++ b/mlair/helpers/filter.py
@@ -768,6 +768,7 @@ class KolmogorovZurbenkoFilterMovingWindow(KolmogorovZurbenkoBaseClass):
 
 
 def firwin_kzf(m, k):
+    m, k = int(m), int(k)
     coef = np.ones(m)
     for i in range(1, k):
         t = np.zeros((m, m + i * (m - 1)))
diff --git a/mlair/plotting/data_insight_plotting.py b/mlair/plotting/data_insight_plotting.py
index 6180493741c030d5dfdfcfa8972035619632c8aa..f7ce47a1b1cf36d4e6d526696d55c7ba2aa4e5f6 100644
--- a/mlair/plotting/data_insight_plotting.py
+++ b/mlair/plotting/data_insight_plotting.py
@@ -21,6 +21,8 @@ from mlair.data_handler import DataCollection
 from mlair.helpers import TimeTrackingWrapper, to_list, remove_items
 from mlair.plotting.abstract_plot_class import AbstractPlotClass
 
+matplotlib.use("Agg")
+
 
 @TimeTrackingWrapper
 class PlotStationMap(AbstractPlotClass):  # pragma: no cover