diff --git a/Makefile b/Makefile
index 365c50f27..a01707a25 100644
--- a/Makefile
+++ b/Makefile
@@ -15,7 +15,7 @@ MAKEFLAGS += --no-print-directory
 
 include ../phoenix-rtos-build/Makefile.common
 
-CFLAGS += -I.
+CFLAGS += -I. -ffreestanding
 CPPFLAGS += -DVERSION=\"$(VERSION)\"
 
 # uncomment to enable stack canary checking
diff --git a/hal/tlb/tlb.c b/hal/tlb/tlb.c
index 92c1c9172..374fc0d0d 100644
--- a/hal/tlb/tlb.c
+++ b/hal/tlb/tlb.c
@@ -82,6 +82,11 @@ void hal_tlbInvalidateEntry(const pmap_t *pmap, const void *vaddr, size_t count)
 	size_t tasks_size;
 	spinlock_ctx_t sc;
 
+	if (id >= MAX_CPU_COUNT) {
+		/* Impossible make gcc array bound checker happy. */
+		return;
+	}
+
 	hal_spinlockSet(&tlb_common.tlbs[id].task_spinlock, &sc);
 	tasks_size = tlb_common.tlbs[id].tasks_size;