diff --git a/ArduCopter/ArduCopter.pde b/ArduCopter/ArduCopter.pde
index 35657cbe973ff25a74eec7f460d2ad2fd9930ec6..d3932f8951df0b125507f9a8db0557b5154efb8c 100644
--- a/ArduCopter/ArduCopter.pde
+++ b/ArduCopter/ArduCopter.pde
@@ -1,6 +1,6 @@
 /// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
 
-#define THISFIRMWARE "ArduCopter V2.9.1"
+#define THISFIRMWARE "ArduCopter V2.9.1b"
 /*
  *  ArduCopter Version 2.9
  *  Lead author:	Jason Short