diff --git a/flake8/run.py b/flake8/run.py
index 222a800..983396e 100644
--- a/flake8/run.py
+++ b/flake8/run.py
@@ -55,8 +55,12 @@ def main():
 
 
 def _get_files(repo, **kwargs):
+    seen = set()
     for rev in xrange(repo[kwargs['node']], len(repo)):
         for file_ in repo[rev].files():
+            if file_ in seen:
+                continue
+            seen.add(file_)
             if not file_.endswith('.py'):
                 continue
             if skip_file(file_):