diff --git a/graphene_mongo/fields.py b/graphene_mongo/fields.py
index 610325e8..08542ff1 100644
--- a/graphene_mongo/fields.py
+++ b/graphene_mongo/fields.py
@@ -121,11 +121,13 @@ def is_filterable(k):
                     ),
             ):
                 return False
-            if getattr(converted, "type", None) and getattr(converted.type, "_of_type", None) and issubclass(
-                    (get_type(converted.type.of_type)), graphene.Union):
+            
+            # Fix for https://github.com/graphql-python/graphene-mongo/issues/162
+            if getattr(converted, "type", None) and getattr(converted.type, "_of_type", None) and not issubclass(
+                    (get_type(converted.type.of_type)), graphene.Scalar):
                 return False
-            if isinstance(converted, (graphene.List)) and issubclass(
-                    getattr(converted, "_of_type", None), graphene.Union
+            if isinstance(converted, (graphene.List)) and not issubclass(
+                    getattr(converted, "_of_type", None), graphene.Scalar
             ):
                 return False
             return True