diff --git a/rowers/utils.py b/rowers/utils.py
index 2656e93d..2617b3ce 100644
--- a/rowers/utils.py
+++ b/rowers/utils.py
@@ -10,6 +10,8 @@ def serialize_list(value,token=','):
 def deserialize_list(value,token=','):
     if isinstance(value, list):
         return value
+    elif isinstance(value, np.ndarray):
+        return value
     return value.split(token)
 
 def geo_distance(lat1,lon1,lat2,lon2):
diff --git a/rowers/views.py b/rowers/views.py
index c6ce4430..e26ca8f9 100644
--- a/rowers/views.py
+++ b/rowers/views.py
@@ -3530,8 +3530,8 @@ def workout_add_otw_powerplot_view(request,id):
 	    'hrtr':r.tr,
 	    'hran':r.an,
 	    'ftp':r.ftp,
-            'powerperc':powerperc,
-            'powerzones':r.powerzones,
+            'powerperc':serialize_list(powerperc),
+            'powerzones':serialize_list(r.powerzones),
 	    }
 
 	# make plot - asynchronous task