From e821b8fa77a756fdcee6b9f18244372d9d477394 Mon Sep 17 00:00:00 2001
From: Junzi Sun <junzisun@gmail.com>
Date: Wed, 4 Apr 2018 10:41:55 +0200
Subject: [PATCH] update roll check

---
 pyModeS/decoder/bds/bds50.py | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/pyModeS/decoder/bds/bds50.py b/pyModeS/decoder/bds/bds50.py
index fc7353b..7f3b212 100644
--- a/pyModeS/decoder/bds/bds50.py
+++ b/pyModeS/decoder/bds/bds50.py
@@ -54,10 +54,9 @@ def is50(msg):
     if wrongstatus(d, 46, 47, 56):
         return False
 
-    if d[1:11] != "0000000000":
-        roll = abs(roll50(msg))
-        if roll and roll > 60:
-            return False
+    roll = roll50(msg)
+    if (roll is not None) and abs(roll) > 60:
+        return False
 
     gs = gs50(msg)
     if gs is not None and gs > 600: