InfiniTime.git

diff --git a/src/FreeRTOS/port_cmsis_systick.c b/src/FreeRTOS/port_cmsis_systick.c
index 58c51bb7bb4dfb5bebec1a64292abd6d3d03bb92..b2cc14cd8277b2666d8fbc5c581f8c702da5a354 100644
--- a/src/FreeRTOS/port_cmsis_systick.c
+++ b/src/FreeRTOS/port_cmsis_systick.c
@@ -251,6 +251,14 @@             }
             else
 #endif
             {
+                // Fix ERRATA 87 (https://infocenter.nordicsemi.com/index.jsp?topic=%252Fcom.nordic.infocenter.sdk5.v11.0.0%252Findex.html&cp=4_0_0)
+                // Clear FPU interrupt before going to sleep. This prevent unexpected wake-up.
+                #define FPU_EXCEPTION_MASK 0x0000009F
+                /* Clear exceptions and PendingIRQ from the FPU unit */
+                __set_FPSCR(__get_FPSCR()  & ~(FPU_EXCEPTION_MASK));
+                (void) __get_FPSCR();
+                NVIC_ClearPendingIRQ(FPU_IRQn);
+
                 /* No SD -  we would just block interrupts globally.
                 * BASEPRI cannot be used for that because it would prevent WFE from wake up.
                 */