diff --git a/wig/classes/output.py b/wig/classes/output.py
index 2b3ba13..68c12d3 100644
--- a/wig/classes/output.py
+++ b/wig/classes/output.py
@@ -96,9 +96,9 @@ def add_error(self, msg):
 		})
 
 	def write_file(self):
-		file_name = self.options['write_file']
-		with open(file_name+ '.json', 'w') as fh:
-			fh.write(json.dumps(self.json_data, sort_keys=True, indent=4, separators=(',', ': ')))
+                file_name = re.sub('(\.json)?\s*$', '', self.options['write_file']) + '.json'
+                with open(file_name, 'w') as fh:
+                    fh.write(json.dumps(self.json_data, sort_keys=True, indent=4, separators=(',', ': ')))
 
 
 class OutputPrinter(Output):