diff --git a/caravel/models.py b/caravel/models.py
index 71824b7fda72..2adb153035e8 100644
--- a/caravel/models.py
+++ b/caravel/models.py
@@ -1410,9 +1410,14 @@ def get_filters(raw_filters):
                 if len(splitted) > 1:
                     for s in eq.split(','):
                         s = s.strip()
+                        if s == 'NULL':
+                            s = None
                         fields.append(Dimension(col) == s)
                     cond = Filter(type="or", fields=fields)
                 else:
+                    #allows setting filter to query that value of dimension is NULL 
+                    if eq == 'NULL':
+                        eq = None
                     cond = Dimension(col) == eq
                 if op == 'not in':
                     cond = ~cond
diff --git a/caravel/viz.py b/caravel/viz.py
index 57ef270a11dd..eb0cc1179866 100755
--- a/caravel/viz.py
+++ b/caravel/viz.py
@@ -177,7 +177,7 @@ def get_df(self, query_obj=None):
                 if self.datasource.offset:
                     df.timestamp += timedelta(hours=self.datasource.offset)
         df.replace([np.inf, -np.inf], np.nan)
-        df = df.fillna(0)
+        df = df.fillna('NULL')
         return df
 
     @property