diff --git a/caravel/views.py b/caravel/views.py
index aea86169c7b..ec25b2d9406 100644
--- a/caravel/views.py
+++ b/caravel/views.py
@@ -551,14 +551,16 @@ class Caravel(BaseView):
             return redirect(error_redirect)
         if request.args.get("json") == "true":
             status = 200
-            try:
+            if config.get("DEBUG"):
+                # Allows for nice debugger stack traces in debug mode
                 payload = obj.get_json()
-            except Exception as e:
-                logging.exception(e)
-                if config.get("DEBUG"):
-                    raise e
-                payload = str(e)
-                status = 500
+            else:
+                try:
+                    payload = obj.get_json()
+                except Exception as e:
+                    logging.exception(e)
+                    payload = str(e)
+                    status = 500
             resp = Response(
                 payload,
                 status=status,
diff --git a/caravel/viz.py b/caravel/viz.py
index 6cc0523931d..ed5d7419f48 100644
--- a/caravel/viz.py
+++ b/caravel/viz.py
@@ -909,6 +909,15 @@ class NVD3TimeSeriesViz(NVD3Viz):
         return df
 
     def to_series(self, df, classed='', title_suffix=''):
+        cols = []
+        for col in df.columns:
+            if col == '':
+                cols.append('N/A')
+            elif col == None:
+                cols.append('NULL')
+            else:
+                cols.append(col)
+        df.columns = cols
         series = df.to_dict('series')
 
         chart_data = []
@@ -931,7 +940,10 @@ class NVD3TimeSeriesViz(NVD3Viz):
             d = {
                 "key": series_title,
                 "classed": classed,
-                "values": [{'x': ds, 'y': ys[ds]} for ds in df.timestamp],
+                "values": [
+                    {'x': ds, 'y': ys[ds] if ds in ys else None}
+                    for ds in df.timestamp
+                ],
             }
             chart_data.append(d)
         return chart_data