diff --git a/ohmpi/ohmpi.py b/ohmpi/ohmpi.py
index 5f3b6d5d136cf7e06f4ebeef014c0ddabcd87239..d15fa18950c3fef354f534a300eac6b594b5dcda 100644
--- a/ohmpi/ohmpi.py
+++ b/ohmpi/ohmpi.py
@@ -196,7 +196,7 @@ class OhmPi(object):
                 mm = np.repeat(last_measurement['M'], dd.shape[0])
                 nn = np.repeat(last_measurement['N'], dd.shape[0])
                 fwdata = np.c_[aa, bb, mm, nn, dd]
-                np.savetxt(f, fwdata, fmt=['%d', '%d', '%d', '%d', '%d', '%d', '%d', '%.3f', '%.3f'])
+                np.savetxt(f, fwdata, fmt=['%d', '%d', '%d', '%d', '%.3f', '%.3f', '%.3f'])
 
         if fw_in_csv:
             d = last_measurement['full_waveform']