diff --git a/arch/sandbox/os/common.c b/arch/sandbox/os/common.c
index 382a923..534571c 100644
--- a/arch/sandbox/os/common.c
+++ b/arch/sandbox/os/common.c
@@ -268,7 +268,7 @@
 	hf->base = (unsigned long)mmap(NULL, hf->size,
 			PROT_READ | (readonly ? 0 : PROT_WRITE),
 			MAP_SHARED, fd, 0);
-	if ((void *)hf->base == MAP_FAILED)
+	if (hf->base == (unsigned long)MAP_FAILED)
 		printf("warning: mmapping %s failed: %s\n", filename, strerror(errno));
 
 	ret = barebox_register_filedev(hf);