diff --git a/ess/TraceWin.py b/ess/TraceWin.py
index a585e622d0e9d1c65f20b7ee70c811c12cfa3bf0..dd8b89da5615338fb4c17d813764b04ce0967ddc 100644
--- a/ess/TraceWin.py
+++ b/ess/TraceWin.py
@@ -199,11 +199,11 @@ class dst:
               }
         # get X and Y data
         dx=np.array(self[x])
-        if mask!=None:
+        if isinstance(mask, np.ndarray):
             dx = dx[mask]
         if y!=None:
             dy = np.array(self[y])
-            if mask!=None:
+            if isinstance(mask, np.ndarray):
                 dy=dy[mask]
 
         if x in ['x','y','xp','yp']:
diff --git a/ess/__init__.py b/ess/__init__.py
index ab1974321918c68446d59f4bd0e2a05d64716471..78299383d12a30f49d8765be2c1189d17aa8a350 100644
--- a/ess/__init__.py
+++ b/ess/__init__.py
@@ -1,5 +1,5 @@
 __all__ = ["fieldmap", "installed", "lib_tw", "SP_Relativity", "TraceWin" "TTF"]
-__version__ = '2.2'
+__version__ = '2.3'
 from . import TraceWin
 from . import installed
 from . import lib_tw