diff --git a/FSStorage.py b/FSStorage.py
index e2428e5..18a19e4 100644
--- a/FSStorage.py
+++ b/FSStorage.py
@@ -27,8 +27,8 @@ mimedict = static.loadMimeTypes()
 
 _klassfuns = []
 
-def registerklassfun(fun):
-	_klassfuns.append(fun)
+def registerklassfun(fun, debug=False):
+	_klassfuns.append((fun, debug))
 
 _filestoignore = {
 		'.DS_Store': None
@@ -237,7 +237,7 @@ def dofileadd(path, name):
 		fobj = open(fsname)
 	except:
 		fobj = None
-	for i in itertools.chain(( ignoreFiles, ), _klassfuns, ( defFS, )):
+	for i, debug in itertools.chain(( (ignoreFiles, False), ), _klassfuns, ( (defFS, False), )):
 		try:
 			try:
 				# incase the call expects a clean file
@@ -250,9 +250,9 @@ def dofileadd(path, name):
 			if klass is not None:
 				break
 		except:
-			#import traceback
-			#traceback.print_exc(file=log.logfile)
-			pass
+			if debug:
+				import traceback
+				traceback.print_exc(file=log.logfile)
 
 	if klass is None or klass is IgnoreFile:
 		return None, None, None, None