diff --git a/python/pysrc/kaskada/_timestream.py b/python/pysrc/kaskada/_timestream.py
index b24d4db38..6c72ff0bc 100644
--- a/python/pysrc/kaskada/_timestream.py
+++ b/python/pysrc/kaskada/_timestream.py
@@ -1216,9 +1216,9 @@ def _aggregation(
         # or a special function to do that.
         #
         # HACK: This places an extra null row in the input to `collect`
-        # which allows us to "clear" the window when the appropriate 
+        # which allows us to "clear" the window when the appropriate
         # `duration` has passed with no "real" inputs.
-        merged_input = record({ "input": input, "shift": input_shift }).col("input")
+        merged_input = record({"input": input, "shift": input_shift}).col("input")
         return Timestream._call("collect", merged_input, *args, None, trailing_ns)
     else:
         raise NotImplementedError(f"Unknown window type {window!r}")