diff --git a/superset/connectors/base.py b/superset/connectors/base.py
index bdb7852f5129a..46bc9581fedb9 100644
--- a/superset/connectors/base.py
+++ b/superset/connectors/base.py
@@ -117,15 +117,24 @@ def __repr__(self):
 
     @property
     def is_num(self):
-        return any([t in self.type.upper() for t in self.num_types])
+        return (
+            self.type and
+            any([t in self.type.upper() for t in self.num_types])
+        )
 
     @property
     def is_time(self):
-        return any([t in self.type.upper() for t in self.date_types])
+        return (
+            self.type and
+            any([t in self.type.upper() for t in self.date_types])
+        )
 
     @property
     def is_string(self):
-        return any([t in self.type.upper() for t in self.str_types])
+        return (
+            self.type and
+            any([t in self.type.upper() for t in self.str_types])
+        )
 
 
 class BaseMetric(AuditMixinNullable, ImportMixin):