diff --git a/hbc b/hbc
index 02217d7..f23e111 100755
--- a/hbc
+++ b/hbc
@@ -213,7 +213,7 @@ def doupdateone(code, csum):
 		return "checksum error"
 
 	fn = sys.argv[0]
-	ofn = "%.sav" % fn
+	ofn = "%s.sav" % fn
 	try:
 		shutil.copy2(fn, ofn)
 	except Exception as e: