diff --git a/commands/go.c b/commands/go.c
index fb319b3..ecc2ceb 100644
--- a/commands/go.c
+++ b/commands/go.c
@@ -45,7 +45,7 @@
 		}
 
 		addr = memmap(fd, PROT_READ);
-		if (addr == (void *)-1) {
+		if (addr == MAP_FAILED) {
 			perror("memmap");
 			goto out;
 		}
diff --git a/commands/md.c b/commands/md.c
index 3e83c72..a495fc8 100644
--- a/commands/md.c
+++ b/commands/md.c
@@ -68,7 +68,7 @@
 		return 1;
 
 	map = memmap(fd, PROT_READ);
-	if (map != (void *)-1) {
+	if (map != MAP_FAILED) {
 		ret = memory_display(map + start, start, size,
 				mode >> O_RWSIZE_SHIFT, swab);
 		goto out;
diff --git a/common/ratp/md.c b/common/ratp/md.c
index 9ce7e99..ce343d7 100644
--- a/common/ratp/md.c
+++ b/common/ratp/md.c
@@ -76,7 +76,7 @@
 		return -errno;
 
 	map = memmap(fd, PROT_READ);
-	if (map != (void *)-1) {
+	if (map != MAP_FAILED) {
 		memcpy(output, (uint8_t *)(map + start), size);
 		goto out;
 	}
diff --git a/crypto/digest.c b/crypto/digest.c
index bc6de0b..b653fbb 100644
--- a/crypto/digest.c
+++ b/crypto/digest.c
@@ -232,7 +232,7 @@
 	}
 
 	buf = memmap(fd, PROT_READ);
-	if (buf == (void *)-1) {
+	if (buf == MAP_FAILED) {
 		buf = xmalloc(4096);
 		flags = 1;
 	}
diff --git a/fs/fs.c b/fs/fs.c
index 625ed10..a304bf1 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -533,7 +533,7 @@
 {
 	struct fs_driver_d *fsdrv;
 	FILE *f;
-	void *retp = (void *)-1;
+	void *retp = MAP_FAILED;
 	int ret;
 
 	if (check_fd(fd))
diff --git a/include/fs.h b/include/fs.h
index 181318f..f1514af 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -130,6 +130,8 @@
 int protect_file(const char *file, int prot);
 void *memmap(int fd, int flags);
 
+#define MAP_FAILED ((void *)-1)
+
 #define FILESIZE_MAX	((loff_t)-1)
 
 #define PROT_READ	1