diff --git a/yamllint/linter.py b/yamllint/linter.py
index cf30cdf7..5501bb59 100644
--- a/yamllint/linter.py
+++ b/yamllint/linter.py
@@ -223,7 +223,7 @@ def run(input, conf, filepath=None):
     :param input: buffer, string or stream to read from
     :param conf: yamllint configuration object
     """
-    if conf.is_file_ignored(filepath):
+    if filepath is not None and conf.is_file_ignored(filepath):
         return ()
 
     if isinstance(input, (bytes, str)):