diff --git a/src/msspec/calcio.py b/src/msspec/calcio.py
index 52fe600..6bb33a2 100644
--- a/src/msspec/calcio.py
+++ b/src/msspec/calcio.py
@@ -907,6 +907,7 @@ class SpecIO(object):
         if content != old_content:
             with open(filename, 'w') as fd:
                 fd.write(content)
+                LOGGER.debug(f"Writing Spec input file written in {filename}")
             modified = True
 
         return modified