diff --git a/dlibrary/dlibrary.py b/dlibrary/dlibrary.py
index 2ef7d32..46da923 100755
--- a/dlibrary/dlibrary.py
+++ b/dlibrary/dlibrary.py
@@ -421,6 +421,8 @@ class Collator:
         if len(srcs) == 0:
             return True
 
+        debug(f'Auto-collating {srcs}')
+
         select_language = self.try_collate_select_language(srcs)
         if select_language is not False:
             return select_language
@@ -544,6 +546,8 @@ class Collator:
         if len(non_images) != 0 or len(images) == 0:
             return False
 
+        debug(f'Comparing PDF {inner_pdf} and images {images}')
+
         pdf_sizes = pdf_image_sizes(inner_pdf)
         standalone_sizes = [standalone_image_size(f) for f in images]
 
@@ -552,6 +556,8 @@ class Collator:
         if not (median_pdf_size and median_standalone_size):
             return False
 
+        debug(f'PDF: {len(pdf_sizes)} images, {median_pdf_size}; standalone: {len(standalone_sizes)} images, median {median_standalone_size}')
+
         if abs(len(pdf_sizes) - len(standalone_sizes)) > 2:
             with fitz.open(inner_pdf) as pdf:
                 pdf_page_count = len(pdf)