diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/bouncebuffer.c b/libraries/AP_HAL_ChibiOS/hwdef/common/bouncebuffer.c
index bd7577fd2f..c9cba5598c 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/bouncebuffer.c
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/bouncebuffer.c
@@ -23,7 +23,7 @@
 
 #if defined(STM32F7) && STM32_DMA_CACHE_HANDLING == TRUE
 // on F7 we check we are in the DTCM region, and 16 bit aligned
-#define IS_DMA_SAFE(addr) ((((uint32_t)(addr)) & 0xFFFE0001) == 0x20000000)
+#define IS_DMA_SAFE(addr) ((((uint32_t)(addr)) & ((0xFFFFFFFF & ~(DTCM_RAM_SIZE_KB*1024U-1)) | 1U)) == 0x20000000)
 #else
 // this checks an address is in main memory and 16 bit aligned
 #define IS_DMA_SAFE(addr) ((((uint32_t)(addr)) & 0xF0000001) == 0x20000000)