diff --git a/HISTORY.rst b/HISTORY.rst
index af16fbf2..0b590869 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -81,7 +81,7 @@ PlatformIO 3.0
 
   + Added support for SODAQ SAMD boards
     (`issue #796 <https://github.com/platformio/platformio-core/issues/796>`__)
-  + Updated ARM mbed OS to 5.1.5/rev127
+  + Updated ARM mbed OS to 5.1.4/rev126
   + Fixed issue with uploading to Arduino Zero on programming USB port
     (`issue #805 <https://github.com/platformio/platformio-core/issues/805>`__)
 
@@ -97,7 +97,7 @@ PlatformIO 3.0
 
 * Development platform `Freescale Kinetis <https://github.com/platformio/platform-freescalekinetis>`__
 
-  + Updated ARM mbed OS to 5.1.5/rev127
+  + Updated ARM mbed OS to 5.1.4/rev126
 
 * Development platform `Microchip PIC32 <https://github.com/platformio/platform-microchippic32>`__
 
@@ -109,24 +109,24 @@ PlatformIO 3.0
 
   + Added BBC micro:bit B(S130) board
     (`issue #3 <https://github.com/platformio/platform-nordicnrf51/issues/3>`__)
-  + Updated ARM mbed OS to 5.1.5/rev127
+  + Updated ARM mbed OS to 5.1.4/rev126
   + Fixed “undefined reference to `_sbrk’” error for RFDuino
     (`issue #1 <https://github.com/platformio/platform-nordicnrf51/issues/1>`__)
 
 * Development platform `NXP LPC <https://github.com/platformio/platform-nxplpc>`__
 
-  + Updated ARM mbed OS to 5.1.5/rev127
+  + Updated ARM mbed OS to 5.1.4/rev126
 
 * Development platform `Silicon Labs EFM32 <https://github.com/platformio/platform-siliconlabsefm32>`__
 
-  + Updated ARM mbed OS to 5.1.5/rev127
+  + Updated ARM mbed OS to 5.1.4/rev126
 
 * Development platform `ST STM32 <https://github.com/platformio/platform-ststm32>`__
 
   + Added support for Maple Mini Original and Maple Mini Bootloader 2.0
     (`issue #22 <https://github.com/platformio/platform-ststm32/issues/22>`__)
   + Added support for new boards: ST 32F769IDISCOVERY
-  + Updated ARM mbed OS to 5.1.5/rev127
+  + Updated ARM mbed OS to 5.1.4/rev126
   + Use ``serial`` protocol by default for STM32Duino-based boards
     (`issue #14 <https://github.com/platformio/platform-ststm32/issues/14>`__)
   + Fixed linker error "undefined reference to _sbrk" for STM32Duino
@@ -135,7 +135,7 @@ PlatformIO 3.0
 * Development platform `Teensy <https://github.com/platformio/platform-teensy>`__
 
   + Updated Arduino Framework for Teensy to v131
-  + Updated ARM mbed OS to 5.1.5/rev127
+  + Updated ARM mbed OS to 5.1.4/rev126
   + Added support for Teensy Audio feature (``build_flags = -D USB_AUDIO``)
 
 * Development platform `TI MSP430 <https://github.com/platformio/platform-timsp430>`__
diff --git a/docs b/docs
index d863d950..3c46771c 160000
--- a/docs
+++ b/docs
@@ -1 +1 @@
-Subproject commit d863d950aede5dfe794032c262ac9509526b57c5
+Subproject commit 3c46771ce0d540c8a80b6e3e2f30588738158a19