diff --git a/src/valon_synth.py b/src/valon_synth.py
index 04822bf..84b8e8d 100644
--- a/src/valon_synth.py
+++ b/src/valon_synth.py
@@ -410,7 +410,10 @@ def get_phase_lock(self, synth):
         checksum = self.conn.read(1)
         self.conn.close()
         #_verify_checksum(data, checksum)
-        mask = (synth << 1) or 0x20
+	if synth == SYNTH_A:
+	  mask = 1 << 4
+	else:
+	  mask = 1 << 5
         lock = struct.unpack('>B', data)[0] & mask
         return lock > 0