diff --git a/sheetsync/sheetsync/main.py b/sheetsync/sheetsync/main.py
index a85595c..0f1811c 100644
--- a/sheetsync/sheetsync/main.py
+++ b/sheetsync/sheetsync/main.py
@@ -128,7 +128,7 @@ class SheetSync(object):
 
 	def parse_bustime(self, value):
 		"""Convert from HH:MM or HH:MM:SS format to datetime"""
-		if value.strip() == '--':
+		if value.strip() in ('--', ''):
 			return None
 		bustime = common.parse_bustime(value)
 		return common.bustime_to_dt(self.bustime_start, bustime)