diff --git a/pdf_oralia/join.py b/pdf_oralia/join.py
index 37c5aea..dcaa5ce 100644
--- a/pdf_oralia/join.py
+++ b/pdf_oralia/join.py
@@ -1,4 +1,5 @@
 import glob
+import logging
 
 import pandas as pd
 
@@ -6,6 +7,7 @@ import pandas as pd
 def join_excel(src, dest, file_pattern):
     """Join every excel file in arc respecting file_pattern into on unique file in dist"""
     filenames = list_files(src, file_pattern)
+    logging.debug(f"Concatenate {filenames}")
     dfs = extract_dfs(filenames)
     joined_df = pd.concat(dfs)
     joined_df.to_excel(dest, index=False)