diff --git a/daqviewer/daqviewer.py b/daqviewer/daqviewer.py
index 4916071..e7b77ee 100644
--- a/daqviewer/daqviewer.py
+++ b/daqviewer/daqviewer.py
@@ -118,8 +118,8 @@ def read_json_data(json_data):
         # Get spectral statistics
         xx = wo.mat2timeseries(np.hstack([t, x]))
         S = xx.tospecdata()
-        S.freqtype = 'f'
         values, _, keys = S.characteristic(range(15))
+        S.freqtype = 'f'
 
         # Update column names
         if dfs.columns[0] == 0: