diff --git a/lib/ansible/plugins/action/include_vars.py b/lib/ansible/plugins/action/include_vars.py
index 22cf07441a..49760a66d1 100644
--- a/lib/ansible/plugins/action/include_vars.py
+++ b/lib/ansible/plugins/action/include_vars.py
@@ -48,7 +48,7 @@ class ActionModule(ActionBase):
         if not self.ignore_files:
             self.ignore_files = list()
 
-        if isinstance(self.ignore_files, str):
+        if isinstance(self.ignore_files, string_types):
             self.ignore_files = self.ignore_files.split()
 
         elif isinstance(self.ignore_files, dict):