diff --git a/hbc b/hbc
index e5888e0..4215b35 100755
--- a/hbc
+++ b/hbc
@@ -245,7 +245,7 @@ def doupdate(conn, msgDict):
 		code = codecs.decode(msgDict['code'],'base64').decode()
 		csum = msgDict['csum']
 	except Exception as e:
-		fail = f"csum/code missing: {e}"
+		fail = "csum/code missing: %s" % e
 	if not fail:
 		fail = doupdateone(code, csum)