diff --git a/gluon/validators.py b/gluon/validators.py
index d94f365d..5142d600 100644
--- a/gluon/validators.py
+++ b/gluon/validators.py
@@ -611,7 +611,7 @@ class IS_IN_DB(Validator):
 
                 def count(values, s=self.dbset, f=field):
                     return s(f.belongs(map(int, values))).count()
-                if isinstance(self.dbset.db._adapter, GoogleDatastoreAdapter):
+                if GoogleDatastoreAdapter is not None and isinstance(self.dbset.db._adapter, GoogleDatastoreAdapter):
                     range_ids = range(0, len(values), 30)
                     total = sum(count(values[i:i + 30]) for i in range_ids)
                     if total == len(values):