diff --git a/ArduSub/ReleaseNotes.txt b/ArduSub/ReleaseNotes.txt
index a807e70854..9b2b2a3e55 100644
--- a/ArduSub/ReleaseNotes.txt
+++ b/ArduSub/ReleaseNotes.txt
@@ -1,5 +1,23 @@
 APM:Sub Release Notes:
 
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Sub 3.5.1beta1 29-August-2017
+
+Changes from 3.5:
+
+- Various parameter metadata and default value corrections
+- Add support for PLAY_TUNE and LED_CONTROL mavlink commands
+- Send sub-specific telemetry via NAMED_VALUE_FLOAT (tether turns, camera tilt angle etc.)
+- Support for Keller LD pressure sensors enabling depth measurement to 200 bar / 2 km
+- Relax arming checks, no sensor checks required by default
+- Increase pilot input failsafe timeout from 1 second to 3 seconds
+- Default INS_GYR_CAL behavior to 'Never' (0)
+- Bug fix neutralization of forward input channel during failsafe
+- Bug fix notify LED status code does not reflect leak fault resolution
+- Set GND_EXT_BUS appropriately at boot for both Pixhawk 1 and Pixhawk 2
+- Bug fix sensor health flag with no pressure sensor detected at boot
+- Acknowledge MAV_CMD_PREFLIGHT_REBOOT_SHUTDOWN before shutting down
+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 Sub 3.5 09-May-2017 / Sub 3.5-rc2 04-May-2017
 
diff --git a/ArduSub/version.h b/ArduSub/version.h
index fd655dbb34..fb224e2fde 100644
--- a/ArduSub/version.h
+++ b/ArduSub/version.h
@@ -2,8 +2,8 @@
 
 #include "ap_version.h"
 
-#define THISFIRMWARE "ArduSub V3.5"
-#define FIRMWARE_VERSION 3,5,0,FIRMWARE_VERSION_TYPE_OFFICIAL
+#define THISFIRMWARE "ArduSub V3.5.1beta1"
+#define FIRMWARE_VERSION 3,5,1,FIRMWARE_VERSION_TYPE_BETA
 
 #ifndef GIT_VERSION
 #define FIRMWARE_STRING THISFIRMWARE