diff --git a/flake8/main.py b/flake8/main.py
index 9e462aa..1241483 100644
--- a/flake8/main.py
+++ b/flake8/main.py
@@ -79,7 +79,7 @@ def check_file(path, ignore=(), complexity=-1):
 def check_code(code, ignore=(), complexity=-1):
     warning = flakey.check(code, '<stdin>')
     warnings = flakey.print_messages(warning, ignore=ignore, code=code)
-    warnings += pep8style.input_file(None, lines=code.split('\n'))
+    warnings += pep8style.input_file('-', lines=code.split('\n'))
     if complexity > -1:
         warnings += mccabe.get_code_complexity(code, complexity)
     return warnings