diff --git a/logmerger/file_reading.py b/logmerger/file_reading.py
index 49e9e6d..56704c0 100644
--- a/logmerger/file_reading.py
+++ b/logmerger/file_reading.py
@@ -273,8 +273,7 @@ def __init__(self, fname: str, encoding: str):
     def _find_dt_col(d: dict[str, Any], previous_key: str | None)-> tuple[str, Any]:
         if previous_key is not None:
             value = d.get(previous_key)
-            if value is not None:
-                return previous_key, value
+            return previous_key, value
         for key, val in d.items():
             try:
                 tt = TimestampedLineTransformer.make_transformer_from_sample_line(str(val) + " ")