diff --git a/superset/viz.py b/superset/viz.py
index f3c7b154ea..769a1af564 100644
--- a/superset/viz.py
+++ b/superset/viz.py
@@ -223,7 +223,7 @@ class BaseViz(object):
         """Converting metrics to numeric when pandas.read_sql cannot"""
         for col, dtype in df.dtypes.items():
             if dtype.type == np.object_ and col in metrics:
-                df[col] = pd.to_numeric(df[col])
+                df[col] = pd.to_numeric(df[col], errors='coerce')
 
     def query_obj(self):
         """Building a query object"""