diff --git a/saqc/flagger/history.py b/saqc/flagger/history.py
index 8a1967ac58315caa794be79d0037780ac5d168da..f7bf9403985bcb25d22d41ac67708b5ec3f70594 100644
--- a/saqc/flagger/history.py
+++ b/saqc/flagger/history.py
@@ -240,9 +240,9 @@ class History:
 
         # shortcut
         if len(self) == n:
+            s = self.max()
             self.hist = pd.DataFrame()
             self.mask = pd.DataFrame()
-            s = self.max()
 
         else:
             # calc the squeezed series.