diff --git a/fowd/cdip.py b/fowd/cdip.py
index 182c094..c96d293 100644
--- a/fowd/cdip.py
+++ b/fowd/cdip.py
@@ -240,6 +240,13 @@ def handle_result(i, result, pbar):
 
     logger.info('Processing done')
 
+    # remove skipped files
+    wave_records = [subrecord for subrecord in wave_records if subrecord is not None]
+
+    if not wave_records:
+        logger.warn('Processed no files - no output to write')
+        return
+
     # concatenate subrecords
     wave_records = {
         key: np.concatenate([subrecord[key] for subrecord in wave_records])