diff --git a/imap_filter/imap_filter.py b/imap_filter/imap_filter.py
index 8a132d7..4a2a5cf 100644
--- a/imap_filter/imap_filter.py
+++ b/imap_filter/imap_filter.py
@@ -227,6 +227,11 @@ class ImapFilter:
                     mfilter
                 )
                 return {"match": False}
+        self._log.debug(
+            "Testing match for '%s' in '%s'...",
+            regexp,
+            field_data
+        )
         match = re.match(regexp, field_data)
         if match:
             self._log.info(