diff --git a/mlinsights/search_rank/search_engine_vectors.py b/mlinsights/search_rank/search_engine_vectors.py
index f3ebba3d..eeec1207 100644
--- a/mlinsights/search_rank/search_engine_vectors.py
+++ b/mlinsights/search_rank/search_engine_vectors.py
@@ -228,7 +228,7 @@ def to_zip(self, zipfilename, **kwargs):
         else:
             zf = zipfilename
             close = False
-        if 'index' is not kwargs:
+        if 'index' not in kwargs:
             kwargs['index'] = False
         to_zip(self.features_, zf, 'SearchEngineVectors-features.npy')
         to_zip(self.metadata_, zf, 'SearchEngineVectors-metadata.csv', **kwargs)