diff --git a/rowers/dataprep.py b/rowers/dataprep.py
index 50397ff7..4277d2ac 100644
--- a/rowers/dataprep.py
+++ b/rowers/dataprep.py
@@ -2534,9 +2534,11 @@ def dataprep(rowdatadf, id=0, bands=True, barchart=True, otwpower=True,
     if id != 0:
         data['workoutid'] = id
         data.fillna(0,inplace=True)
-        data = data.astype(
-            dtype=dtypes,
-             )
+        for k, v in dtypes.items():
+            try:
+                data[k] = data[k].astype(v)
+            except KeyError:
+                pass
 
 
         filename = 'media/strokedata_{id}.parquet.gz'.format(id=id)
diff --git a/rowers/dataprepnodjango.py b/rowers/dataprepnodjango.py
index cdf2580a..bdd1f162 100644
--- a/rowers/dataprepnodjango.py
+++ b/rowers/dataprepnodjango.py
@@ -1254,7 +1254,13 @@ def dataprep(rowdatadf,id=0,bands=True,barchart=True,otwpower=True,
     # write data if id given
     if id != 0:
         data['workoutid'] = id
-        data = data.astype(dtype=dtypes)
+        data.fillna(0,inplace=True)
+        for k, v in dtypes.items():
+            try:
+                data[k] = data[k].astype(v) 
+            except KeyError:
+                pass
+
         filename = 'media/strokedata_{id}.parquet.gz'.format(id=id)
         df = dd.from_pandas(data,npartitions=1)
         df.to_parquet(filename,engine='fastparquet',compression='GZIP')