diff --git a/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c b/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c
index 6703f278c9..0ea409c601 100644
--- a/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c
+++ b/libraries/AP_HAL_ChibiOS/hwdef/common/malloc.c
@@ -52,7 +52,9 @@ static memory_heap_t dtcm_heap;
 #define DMA_RESERVE_SIZE 4096
 #endif
 
+#if DMA_RESERVE_SIZE != 0
 static memory_heap_t dma_reserve_heap;
+#endif
 
 static void *malloc_dtcm(size_t size);