diff --git a/woudc_data_registry/search.py b/woudc_data_registry/search.py
index 714432a..4559a0d 100644
--- a/woudc_data_registry/search.py
+++ b/woudc_data_registry/search.py
@@ -1079,7 +1079,7 @@ def generate_index_name(self, index_name):
         """
 
         if self.index_basename is not None:
-            return 'f{self.index_basename}.{index_name}'
+            return f'{self.index_basename}.{index_name}'
 
         return index_name