diff --git a/pyModeS/decoder/bds/bds09.py b/pyModeS/decoder/bds/bds09.py
index 641f53c..fcb24e3 100644
--- a/pyModeS/decoder/bds/bds09.py
+++ b/pyModeS/decoder/bds/bds09.py
@@ -74,8 +74,9 @@ def airborne_velocity(msg):
             hdg = None
         else:
             hdg = common.bin2int(mb[14:24]) / 1024.0 * 360.0
+            hdg = round(hdg, 2)
 
-        trk_or_hdg = round(hdg, 2)
+        trk_or_hdg = hdg
 
         spd = common.bin2int(mb[25:35])
         spd = None if spd==0 else spd-1
diff --git a/pyModeS/streamer/stream.py b/pyModeS/streamer/stream.py
index 947f4af..f139bfd 100644
--- a/pyModeS/streamer/stream.py
+++ b/pyModeS/streamer/stream.py
@@ -61,6 +61,8 @@ class Stream():
                 spd, trk, roc, tag = vdata
                 if tag != 'GS':
                     continue
+                if (spd is None) or (trk is None):
+                    continue
 
                 self.acs[icao]['gs'] = spd
                 self.acs[icao]['trk'] = trk